Prefix leveldb debug logging
Prefix leveldb debug logging

Add leveldb: prefix to leveldb debug logging lines.
leveldb debug messages come in various scary flavors such as:

    2017-11-30 08:26:31 leveldb: Recovering log #26
    2017-11-30 08:26:31 leveldb: Level-0 table #28: started
    2017-11-30 08:26:31 leveldb: Level-0 table #28: 597 bytes OK
    2017-11-30 08:26:31 leveldb: Delete type=0 #26
    2017-11-30 08:26:31 leveldb: Delete type=3 #24

so it's reasonably important to mark them as coming from leveldb
internals and not from consensus validation wallet or such.

(this only affects `-debug=leveldb` or `-debug=1` otherwise you won't
see them in the first place)

namecoin/namecore,domob1812/huntercore,jonasschnelli/bitcoin,bespike/litecoin,cdecker/bitcoin,particl/particl-core,alecalve/bitcoin,Kogser/bitcoin,laudaa/bitcoin,practicalswift/bitcoin,fanquake/bitcoin,brandonrobertz/namecoin-core,mb300sd/bitcoin,lateminer/bitcoin,kallewoof/bitcoin,deeponion/deeponion,jambolo/bitcoin,Rav3nPL/bitcoin,gjhiggins/vcoincore,domob1812/bitcoin,ahmedbodi/vertcoin,rnicoll/bitcoin,Flowdalic/bitcoin,h4x3rotab/BTCGPU,afk11/bitcoin,ryanofsky/bitcoin,ericshawlinux/bitcoin,dscotese/bitcoin,mitchellcash/bitcoin,joshrabinowitz/bitcoin,ahmedbodi/vertcoin,midnightmagic/bitcoin,pataquets/namecoin-core,qtumproject/qtum,pstratem/bitcoin,kazcw/bitcoin,brandonrobertz/namecoin-core,tecnovert/particl-core,jnewbery/bitcoin,ajtowns/bitcoin,domob1812/huntercore,alecalve/bitcoin,jmcorgan/bitcoin,Sjors/bitcoin,prusnak/bitcoin,bespike/litecoin,paveljanik/bitcoin,starwels/starwels,digibyte/digibyte,rawodb/bitcoin,ericshawlinux/bitcoin,guncoin/guncoin,afk11/bitcoin,jamesob/bitcoin,bitcoinknots/bitcoin,mb300sd/bitcoin,r8921039/bitcoin,pstratem/bitcoin,laudaa/bitcoin,viacoin/viacoin,GlobalBoost/GlobalBoost,ryanofsky/bitcoin,jlopp/statoshi,randy-waterhouse/bitcoin,vertcoin/vertcoin,Rav3nPL/bitcoin,litecoin-project/litecoin,rnicoll/dogecoin,1185/starwels,maaku/bitcoin,globaltoken/globaltoken,ahmedbodi/vertcoin,rnicoll/bitcoin,digibyte/digibyte,ericshawlinux/bitcoin,dscotese/bitcoin,TheBlueMatt/bitcoin,lbryio/lbrycrd,AkioNak/bitcoin,apoelstra/bitcoin,Christewart/bitcoin,lateminer/bitcoin,lbryio/lbrycrd,particl/particl-core,andreaskern/bitcoin,rawodb/bitcoin,fujicoin/fujicoin,jtimon/bitcoin,sipsorcery/bitcoin,tecnovert/particl-core,andreaskern/bitcoin,sebrandon1/bitcoin,wellenreiter01/Feathercoin,droark/bitcoin,tecnovert/particl-core,andreaskern/bitcoin,stamhe/bitcoin,deeponion/deeponion,MeshCollider/bitcoin,kazcw/bitcoin,jmcorgan/bitcoin,litecoin-project/litecoin,nikkitan/bitcoin,practicalswift/bitcoin,EthanHeilman/bitcoin,fujicoin/fujicoin,yenliangl/bitcoin,FeatherCoin/Feathercoin,GroestlCoin/GroestlCoin,maaku/bitcoin,GlobalBoost/GlobalBoost,FeatherCoin/Feathercoin,jamesob/bitcoin,peercoin/peercoin,ppcoin/ppcoin,guncoin/guncoin,myriadcoin/myriadcoin,fanquake/bitcoin,jmcorgan/bitcoin,untrustbank/litecoin,Flowdalic/bitcoin,domob1812/huntercore,RHavar/bitcoin,MarcoFalke/bitcoin,Kogser/bitcoin,randy-waterhouse/bitcoin,bitcoin/bitcoin,kazcw/bitcoin,globaltoken/globaltoken,MarcoFalke/bitcoin,andreaskern/bitcoin,Kogser/bitcoin,h4x3rotab/BTCGPU,MeshCollider/bitcoin,ryanofsky/bitcoin,Kogser/bitcoin,achow101/bitcoin,jambolo/bitcoin,guncoin/guncoin,MazaCoin/maza,bitcoinsSG/bitcoin,rnicoll/bitcoin,rawodb/bitcoin,anditto/bitcoin,Christewart/bitcoin,thrasher-/litecoin,pataquets/namecoin-core,bespike/litecoin,domob1812/bitcoin,donaloconnor/bitcoin,ElementsProject/elements,stamhe/bitcoin,Kogser/bitcoin,n1bor/bitcoin,anditto/bitcoin,r8921039/bitcoin,jlopp/statoshi,MarcoFalke/bitcoin,namecoin/namecoin-core,bitcoinsSG/bitcoin,mitchellcash/bitcoin,Rav3nPL/bitcoin,vmp32k/litecoin,EthanHeilman/bitcoin,domob1812/huntercore,particl/particl-core,donaloconnor/bitcoin,MeshCollider/bitcoin,MeshCollider/bitcoin,peercoin/peercoin,tjps/bitcoin,h4x3rotab/BTCGPU,Bushstar/UFO-Project,cdecker/bitcoin,BTCGPU/BTCGPU,randy-waterhouse/bitcoin,Bushstar/UFO-Project,Bushstar/UFO-Project,RHavar/bitcoin,practicalswift/bitcoin,achow101/bitcoin,rnicoll/dogecoin,dscotese/bitcoin,myriadteam/myriadcoin,jtimon/bitcoin,Bushstar/UFO-Project,Xekyo/bitcoin,joshrabinowitz/bitcoin,domob1812/bitcoin,practicalswift/bitcoin,CryptArc/bitcoin,prusnak/bitcoin,instagibbs/bitcoin,bitcoinknots/bitcoin,stamhe/bitcoin,h4x3rotab/BTCGPU,jnewbery/bitcoin,wellenreiter01/Feathercoin,anditto/bitcoin,randy-waterhouse/bitcoin,sebrandon1/bitcoin,namecoin/namecore,cdecker/bitcoin,ppcoin/ppcoin,MazaCoin/maza,midnightmagic/bitcoin,afk11/bitcoin,midnightmagic/bitcoin,vmp32k/litecoin,Christewart/bitcoin,r8921039/bitcoin,pstratem/bitcoin,domob1812/namecore,pstratem/bitcoin,h4x3rotab/BTCGPU,JeremyRubin/bitcoin,domob1812/namecore,prusnak/bitcoin,jtimon/bitcoin,ElementsProject/elements,EthanHeilman/bitcoin,ericshawlinux/bitcoin,FeatherCoin/Feathercoin,laudaa/bitcoin,myriadcoin/myriadcoin,DigitalPandacoin/pandacoin,viacoin/viacoin,particl/particl-core,bitcoin/bitcoin,andreaskern/bitcoin,rnicoll/dogecoin,cdecker/bitcoin,tjps/bitcoin,MazaCoin/maza,achow101/bitcoin,pataquets/namecoin-core,jamesob/bitcoin,alecalve/bitcoin,GlobalBoost/GlobalBoost,joshrabinowitz/bitcoin,jtimon/bitcoin,untrustbank/litecoin,donaloconnor/bitcoin,Kogser/bitcoin,jamesob/bitcoin,instagibbs/bitcoin,litecoin-project/litecoin,lateminer/bitcoin,namecoin/namecore,laudaa/bitcoin,mb300sd/bitcoin,jamesob/bitcoin,paveljanik/bitcoin,tecnovert/particl-core,pstratem/bitcoin,myriadteam/myriadcoin,peercoin/peercoin,wellenreiter01/Feathercoin,globaltoken/globaltoken,prusnak/bitcoin,OmniLayer/omnicore,practicalswift/bitcoin,jlopp/statoshi,pataquets/namecoin-core,maaku/bitcoin,qtumproject/qtum,maaku/bitcoin,n1bor/bitcoin,MazaCoin/maza,MarcoFalke/bitcoin,midnightmagic/bitcoin,jamesob/bitcoin,sebrandon1/bitcoin,tecnovert/particl-core,Christewart/bitcoin,thrasher-/litecoin,nikkitan/bitcoin,qtumproject/qtum,thrasher-/litecoin,starwels/starwels,deeponion/deeponion,TheBlueMatt/bitcoin,maaku/bitcoin,ahmedbodi/vertcoin,particl/particl-core,jmcorgan/bitcoin,ajtowns/bitcoin,jtimon/bitcoin,rnicoll/dogecoin,ahmedbodi/vertcoin,ajtowns/bitcoin,mruddy/bitcoin,tjps/bitcoin,droark/bitcoin,thrasher-/litecoin,sstone/bitcoin,n1bor/bitcoin,GroestlCoin/bitcoin,1185/starwels,globaltoken/globaltoken,mm-s/bitcoin,rnicoll/bitcoin,rnicoll/bitcoin,apoelstra/bitcoin,mruddy/bitcoin,sipsorcery/bitcoin,kallewoof/bitcoin,sstone/bitcoin,GlobalBoost/GlobalBoost,Kogser/bitcoin,RHavar/bitcoin,namecoin/namecoin-core,pataquets/namecoin-core,afk11/bitcoin,r8921039/bitcoin,kazcw/bitcoin,AkioNak/bitcoin,kazcw/bitcoin,BTCGPU/BTCGPU,fanquake/bitcoin,anditto/bitcoin,JeremyRubin/bitcoin,domob1812/namecore,kallewoof/bitcoin,1185/starwels,myriadcoin/myriadcoin,fanquake/bitcoin,sstone/bitcoin,GroestlCoin/bitcoin,untrustbank/litecoin,jmcorgan/bitcoin,1185/starwels,droark/bitcoin,pstratem/bitcoin,untrustbank/litecoin,peercoin/peercoin,alecalve/bitcoin,r8921039/bitcoin,bitcoinsSG/bitcoin,Bushstar/UFO-Project,domob1812/namecore,guncoin/guncoin,vertcoin/vertcoin,bitcoin/bitcoin,namecoin/namecore,pataquets/namecoin-core,fujicoin/fujicoin,vmp32k/litecoin,GroestlCoin/GroestlCoin,jambolo/bitcoin,bitcoin/bitcoin,Xekyo/bitcoin,viacoin/viacoin,mitchellcash/bitcoin,deeponion/deeponion,Christewart/bitcoin,alecalve/bitcoin,monacoinproject/monacoin,ElementsProject/elements,jlopp/statoshi,BTCGPU/BTCGPU,nikkitan/bitcoin,bitcoinsSG/bitcoin,nikkitan/bitcoin,peercoin/peercoin,paveljanik/bitcoin,OmniLayer/omnicore,rawodb/bitcoin,Xekyo/bitcoin,donaloconnor/bitcoin,h4x3rotab/BTCGPU,wellenreiter01/Feathercoin,lateminer/bitcoin,sstone/bitcoin,DigitalPandacoin/pandacoin,ajtowns/bitcoin,deeponion/deeponion,joshrabinowitz/bitcoin,GroestlCoin/GroestlCoin,Xekyo/bitcoin,randy-waterhouse/bitcoin,bitcoin/bitcoin,qtumproject/qtum,mb300sd/bitcoin,qtumproject/qtum,Kogser/bitcoin,sstone/bitcoin,JeremyRubin/bitcoin,jnewbery/bitcoin,jonasschnelli/bitcoin,laudaa/bitcoin,brandonrobertz/namecoin-core,achow101/bitcoin,prusnak/bitcoin,CryptArc/bitcoin,stamhe/bitcoin,yenliangl/bitcoin,CryptArc/bitcoin,globaltoken/globaltoken,myriadteam/myriadcoin,FeatherCoin/Feathercoin,untrustbank/litecoin,untrustbank/litecoin,deeponion/deeponion,digibyte/digibyte,randy-waterhouse/bitcoin,BTCGPU/BTCGPU,AkioNak/bitcoin,andreaskern/bitcoin,mm-s/bitcoin,jambolo/bitcoin,mitchellcash/bitcoin,MazaCoin/maza,Rav3nPL/bitcoin,fanquake/bitcoin,bitcoinknots/bitcoin,paveljanik/bitcoin,brandonrobertz/namecoin-core,jlopp/statoshi,mruddy/bitcoin,apoelstra/bitcoin,gjhiggins/vcoincore,mb300sd/bitcoin,JeremyRubin/bitcoin,OmniLayer/omnicore,starwels/starwels,guncoin/guncoin,midnightmagic/bitcoin,jambolo/bitcoin,globaltoken/globaltoken,bitcoinsSG/bitcoin,r8921039/bitcoin,ElementsProject/elements,ppcoin/ppcoin,sipsorcery/bitcoin,gjhiggins/vcoincore,myriadteam/myriadcoin,MeshCollider/bitcoin,AkioNak/bitcoin,viacoin/viacoin,maaku/bitcoin,DigitalPandacoin/pandacoin,vmp32k/litecoin,fujicoin/fujicoin,sipsorcery/bitcoin,ahmedbodi/vertcoin,EthanHeilman/bitcoin,litecoin-project/litecoin,ElementsProject/elements,bitcoinsSG/bitcoin,kallewoof/bitcoin,namecoin/namecoin-core,donaloconnor/bitcoin,Flowdalic/bitcoin,litecoin-project/litecoin,instagibbs/bitcoin,mruddy/bitcoin,BTCGPU/BTCGPU,CryptArc/bitcoin,brandonrobertz/namecoin-core,mruddy/bitcoin,alecalve/bitcoin,cdecker/bitcoin,domob1812/namecore,jonasschnelli/bitcoin,GroestlCoin/bitcoin,ericshawlinux/bitcoin,tecnovert/particl-core,kazcw/bitcoin,monacoinproject/monacoin,RHavar/bitcoin,ppcoin/ppcoin,mruddy/bitcoin,donaloconnor/bitcoin,JeremyRubin/bitcoin,mm-s/bitcoin,mm-s/bitcoin,afk11/bitcoin,Xekyo/bitcoin,achow101/bitcoin,fujicoin/fujicoin,thrasher-/litecoin,GroestlCoin/GroestlCoin,anditto/bitcoin,TheBlueMatt/bitcoin,cdecker/bitcoin,TheBlueMatt/bitcoin,digibyte/digibyte,thrasher-/litecoin,jnewbery/bitcoin,prusnak/bitcoin,domob1812/namecore,gjhiggins/vcoincore,namecoin/namecoin-core,n1bor/bitcoin,GlobalBoost/GlobalBoost,sebrandon1/bitcoin,1185/starwels,lateminer/bitcoin,bitcoinknots/bitcoin,jlopp/statoshi,myriadcoin/myriadcoin,Bushstar/UFO-Project,RHavar/bitcoin,kallewoof/bitcoin,sebrandon1/bitcoin,Sjors/bitcoin,domob1812/huntercore,rawodb/bitcoin,DigitalPandacoin/pandacoin,Sjors/bitcoin,sstone/bitcoin,namecoin/namecore,stamhe/bitcoin,ajtowns/bitcoin,paveljanik/bitcoin,EthanHeilman/bitcoin,GroestlCoin/bitcoin,jonasschnelli/bitcoin,lbryio/lbrycrd,jmcorgan/bitcoin,nikkitan/bitcoin,digibyte/digibyte,mitchellcash/bitcoin,bitcoinknots/bitcoin,domob1812/bitcoin,paveljanik/bitcoin,tjps/bitcoin,namecoin/namecoin-core,mb300sd/bitcoin,wellenreiter01/Feathercoin,monacoinproject/monacoin,GroestlCoin/GroestlCoin,litecoin-project/litecoin,qtumproject/qtum,starwels/starwels,sebrandon1/bitcoin,OmniLayer/omnicore,apoelstra/bitcoin,vmp32k/litecoin,tjps/bitcoin,myriadteam/myriadcoin,laudaa/bitcoin,namecoin/namecore,bitcoin/bitcoin,jnewbery/bitcoin,MarcoFalke/bitcoin,Kogser/bitcoin,nikkitan/bitcoin,kallewoof/bitcoin,JeremyRubin/bitcoin,apoelstra/bitcoin,droark/bitcoin,sipsorcery/bitcoin,bespike/litecoin,Sjors/bitcoin,Flowdalic/bitcoin,fanquake/bitcoin,AkioNak/bitcoin,ajtowns/bitcoin,Christewart/bitcoin,lbryio/lbrycrd,rawodb/bitcoin,CryptArc/bitcoin,sipsorcery/bitcoin,domob1812/bitcoin,guncoin/guncoin,droark/bitcoin,Kogser/bitcoin,DigitalPandacoin/pandacoin,lbryio/lbrycrd,rnicoll/bitcoin,midnightmagic/bitcoin,RHavar/bitcoin,wellenreiter01/Feathercoin,jambolo/bitcoin,viacoin/viacoin,Sjors/bitcoin,qtumproject/qtum,Xekyo/bitcoin,peercoin/peercoin,anditto/bitcoin,stamhe/bitcoin,monacoinproject/monacoin,vertcoin/vertcoin,myriadcoin/myriadcoin,jonasschnelli/bitcoin,monacoinproject/monacoin,afk11/bitcoin,lbryio/lbrycrd,mm-s/bitcoin,TheBlueMatt/bitcoin,apoelstra/bitcoin,Kogser/bitcoin,vmp32k/litecoin,monacoinproject/monacoin,GlobalBoost/GlobalBoost,ericshawlinux/bitcoin,droark/bitcoin,brandonrobertz/namecoin-core,1185/starwels,myriadcoin/myriadcoin,rnicoll/dogecoin,instagibbs/bitcoin,domob1812/huntercore,yenliangl/bitcoin,ryanofsky/bitcoin,gjhiggins/vcoincore,digibyte/digibyte,AkioNak/bitcoin,n1bor/bitcoin,n1bor/bitcoin,TheBlueMatt/bitcoin,instagibbs/bitcoin,MazaCoin/maza,OmniLayer/omnicore,MeshCollider/bitcoin,mm-s/bitcoin,particl/particl-core,starwels/starwels,Rav3nPL/bitcoin,DigitalPandacoin/pandacoin,GroestlCoin/bitcoin,viacoin/viacoin,lbryio/lbrycrd,vertcoin/vertcoin,yenliangl/bitcoin,GroestlCoin/bitcoin,tjps/bitcoin,OmniLayer/omnicore,bespike/litecoin,jtimon/bitcoin,ElementsProject/elements,ryanofsky/bitcoin,starwels/starwels,joshrabinowitz/bitcoin,practicalswift/bitcoin,fujicoin/fujicoin,FeatherCoin/Feathercoin,dscotese/bitcoin,yenliangl/bitcoin,joshrabinowitz/bitcoin,CryptArc/bitcoin,achow101/bitcoin,GroestlCoin/GroestlCoin,Flowdalic/bitcoin,MarcoFalke/bitcoin,ryanofsky/bitcoin,yenliangl/bitcoin,myriadteam/myriadcoin,FeatherCoin/Feathercoin,instagibbs/bitcoin,bespike/litecoin,domob1812/bitcoin,BTCGPU/BTCGPU,namecoin/namecoin-core,Kogser/bitcoin,dscotese/bitcoin,vertcoin/vertcoin,mitchellcash/bitcoin,vertcoin/vertcoin,lateminer/bitcoin,EthanHeilman/bitcoin,dscotese/bitcoin,Rav3nPL/bitcoin,gjhiggins/vcoincore,GlobalBoost/GlobalBoost,Flowdalic/bitcoin