bug-fix macos: give free bytes to F_PREALLOCATE
bug-fix macos: give free bytes to F_PREALLOCATE

The macos manpage for fcntl (for F_PEOFPOSMODE) states:

> Allocate from the physical end of file.  In this case, fst_length indicates the number of newly allocated bytes desired.

instagibbs/bitcoin,kallewoof/bitcoin,namecoin/namecoin-core,DigitalPandacoin/pandacoin,bitcoinknots/bitcoin,namecoin/namecore,MarcoFalke/bitcoin,n1bor/bitcoin,vertcoin/vertcoin,EthanHeilman/bitcoin,jamesob/bitcoin,domob1812/bitcoin,MeshCollider/bitcoin,MeshCollider/bitcoin,MeshCollider/bitcoin,peercoin/peercoin,anditto/bitcoin,practicalswift/bitcoin,achow101/bitcoin,mm-s/bitcoin,ElementsProject/elements,midnightmagic/bitcoin,ahmedbodi/vertcoin,anditto/bitcoin,n1bor/bitcoin,MarcoFalke/bitcoin,mm-s/bitcoin,anditto/bitcoin,cdecker/bitcoin,pataquets/namecoin-core,rnicoll/dogecoin,litecoin-project/litecoin,mitchellcash/bitcoin,namecoin/namecore,fujicoin/fujicoin,Xekyo/bitcoin,lateminer/bitcoin,bitcoin/bitcoin,instagibbs/bitcoin,alecalve/bitcoin,GroestlCoin/GroestlCoin,n1bor/bitcoin,lateminer/bitcoin,jlopp/statoshi,sstone/bitcoin,achow101/bitcoin,ahmedbodi/vertcoin,practicalswift/bitcoin,jnewbery/bitcoin,andreaskern/bitcoin,cdecker/bitcoin,kallewoof/bitcoin,apoelstra/bitcoin,achow101/bitcoin,midnightmagic/bitcoin,GroestlCoin/bitcoin,JeremyRubin/bitcoin,tecnovert/particl-core,jnewbery/bitcoin,particl/particl-core,vertcoin/vertcoin,GroestlCoin/GroestlCoin,fanquake/bitcoin,gjhiggins/vcoincore,JeremyRubin/bitcoin,jambolo/bitcoin,litecoin-project/litecoin,JeremyRubin/bitcoin,ahmedbodi/vertcoin,pstratem/bitcoin,GroestlCoin/GroestlCoin,jambolo/bitcoin,sipsorcery/bitcoin,cdecker/bitcoin,sipsorcery/bitcoin,rnicoll/dogecoin,achow101/bitcoin,alecalve/bitcoin,jlopp/statoshi,instagibbs/bitcoin,monacoinproject/monacoin,litecoin-project/litecoin,jonasschnelli/bitcoin,apoelstra/bitcoin,kallewoof/bitcoin,GroestlCoin/bitcoin,fanquake/bitcoin,AkioNak/bitcoin,prusnak/bitcoin,dscotese/bitcoin,monacoinproject/monacoin,sipsorcery/bitcoin,andreaskern/bitcoin,kallewoof/bitcoin,jamesob/bitcoin,jnewbery/bitcoin,cdecker/bitcoin,namecoin/namecore,rnicoll/bitcoin,sstone/bitcoin,MarcoFalke/bitcoin,domob1812/bitcoin,jambolo/bitcoin,bitcoinknots/bitcoin,pataquets/namecoin-core,jonasschnelli/bitcoin,pstratem/bitcoin,lateminer/bitcoin,MarcoFalke/bitcoin,instagibbs/bitcoin,apoelstra/bitcoin,yenliangl/bitcoin,mitchellcash/bitcoin,particl/particl-core,ElementsProject/elements,ElementsProject/elements,tecnovert/particl-core,EthanHeilman/bitcoin,anditto/bitcoin,namecoin/namecoin-core,DigitalPandacoin/pandacoin,andreaskern/bitcoin,midnightmagic/bitcoin,domob1812/namecore,bitcoinsSG/bitcoin,GroestlCoin/bitcoin,achow101/bitcoin,rnicoll/dogecoin,sstone/bitcoin,MarcoFalke/bitcoin,ahmedbodi/vertcoin,prusnak/bitcoin,n1bor/bitcoin,monacoinproject/monacoin,practicalswift/bitcoin,EthanHeilman/bitcoin,jlopp/statoshi,alecalve/bitcoin,domob1812/bitcoin,vertcoin/vertcoin,alecalve/bitcoin,qtumproject/qtum,jlopp/statoshi,bitcoin/bitcoin,mm-s/bitcoin,mitchellcash/bitcoin,bitcoin/bitcoin,anditto/bitcoin,instagibbs/bitcoin,kallewoof/bitcoin,rnicoll/bitcoin,ajtowns/bitcoin,litecoin-project/litecoin,pataquets/namecoin-core,MeshCollider/bitcoin,mruddy/bitcoin,gjhiggins/vcoincore,dscotese/bitcoin,mruddy/bitcoin,pataquets/namecoin-core,pataquets/namecoin-core,domob1812/bitcoin,AkioNak/bitcoin,alecalve/bitcoin,JeremyRubin/bitcoin,jamesob/bitcoin,practicalswift/bitcoin,midnightmagic/bitcoin,ajtowns/bitcoin,kallewoof/bitcoin,jambolo/bitcoin,bitcoinknots/bitcoin,prusnak/bitcoin,sstone/bitcoin,monacoinproject/monacoin,rnicoll/dogecoin,sstone/bitcoin,jamesob/bitcoin,tecnovert/particl-core,dscotese/bitcoin,JeremyRubin/bitcoin,n1bor/bitcoin,DigitalPandacoin/pandacoin,apoelstra/bitcoin,GroestlCoin/bitcoin,mruddy/bitcoin,lateminer/bitcoin,andreaskern/bitcoin,cdecker/bitcoin,domob1812/bitcoin,qtumproject/qtum,yenliangl/bitcoin,bitcoin/bitcoin,jonasschnelli/bitcoin,peercoin/peercoin,pstratem/bitcoin,lateminer/bitcoin,Sjors/bitcoin,Sjors/bitcoin,jonasschnelli/bitcoin,namecoin/namecore,yenliangl/bitcoin,namecoin/namecoin-core,ajtowns/bitcoin,AkioNak/bitcoin,yenliangl/bitcoin,bitcoinsSG/bitcoin,andreaskern/bitcoin,GroestlCoin/bitcoin,andreaskern/bitcoin,Xekyo/bitcoin,monacoinproject/monacoin,AkioNak/bitcoin,GroestlCoin/GroestlCoin,gjhiggins/vcoincore,namecoin/namecore,bitcoinsSG/bitcoin,yenliangl/bitcoin,bitcoinknots/bitcoin,particl/particl-core,cdecker/bitcoin,ahmedbodi/vertcoin,qtumproject/qtum,peercoin/peercoin,practicalswift/bitcoin,jlopp/statoshi,jambolo/bitcoin,DigitalPandacoin/pandacoin,n1bor/bitcoin,sipsorcery/bitcoin,dscotese/bitcoin,DigitalPandacoin/pandacoin,vertcoin/vertcoin,fanquake/bitcoin,namecoin/namecore,achow101/bitcoin,bitcoin/bitcoin,sipsorcery/bitcoin,jambolo/bitcoin,fujicoin/fujicoin,prusnak/bitcoin,namecoin/namecoin-core,bitcoinsSG/bitcoin,Sjors/bitcoin,domob1812/namecore,tecnovert/particl-core,Xekyo/bitcoin,fujicoin/fujicoin,prusnak/bitcoin,ahmedbodi/vertcoin,EthanHeilman/bitcoin,jamesob/bitcoin,vertcoin/vertcoin,yenliangl/bitcoin,Xekyo/bitcoin,namecoin/namecoin-core,apoelstra/bitcoin,particl/particl-core,particl/particl-core,namecoin/namecoin-core,bitcoinknots/bitcoin,ElementsProject/elements,ElementsProject/elements,fanquake/bitcoin,qtumproject/qtum,pstratem/bitcoi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