p2p: declare Announcement::m_state as uint8_t, add getter/setter
p2p: declare Announcement::m_state as uint8_t, add getter/setter

to silence these Travis CI GCC compiler warnings:

txrequest.cpp:73:21: warning: ‘{anonymous}::Announcement::m_state’ is
too small to hold all values of ‘enum class {anonymous}::State’
     State m_state : 3;
                     ^
The warnings are based on the maximum value held by the underlying uint8_t
enumerator type, though the intention of the bitfield declaration is the
maximum declared enumerator value.

The warning been silenced in GCC 8.4+ and 9.3+ according to
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61414

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