Revert "Avoid the use of P0083R3 std::set::merge"
Revert "Avoid the use of P0083R3 std::set::merge"

This reverts commit 6cf4ea71878c0a83f2e49831e4dfa119c53761b7.

ajtowns/bitcoin,ajtowns/bitcoin,sstone/bitcoin,bitcoin/bitcoin,bitcoinsSG/bitcoin,achow101/bitcoin,bitcoin/bitcoin,mruddy/bitcoin,fujicoin/fujicoin,jambolo/bitcoin,kallewoof/bitcoin,tecnovert/particl-core,jambolo/bitcoin,instagibbs/bitcoin,bitcoinsSG/bitcoin,namecoin/namecoin-core,domob1812/bitcoin,namecoin/namecoin-core,andreaskern/bitcoin,particl/particl-core,domob1812/bitcoin,andreaskern/bitcoin,sstone/bitcoin,particl/particl-core,anditto/bitcoin,bitcoinsSG/bitcoin,fanquake/bitcoin,jamesob/bitcoin,namecoin/namecore,jlopp/statoshi,namecoin/namecoin-core,GroestlCoin/GroestlCoin,jambolo/bitcoin,GroestlCoin/GroestlCoin,jlopp/statoshi,AkioNak/bitcoin,sstone/bitcoin,bitcoin/bitcoin,particl/particl-core,andreaskern/bitcoin,AkioNak/bitcoin,tecnovert/particl-core,namecoin/namecore,jamesob/bitcoin,jamesob/bitcoin,bitcoin/bitcoin,ajtowns/bitcoin,andreaskern/bitcoin,sstone/bitcoin,bitcoinsSG/bitcoin,instagibbs/bitcoin,dscotese/bitcoin,namecoin/namecore,bitcoin/bitcoin,achow101/bitcoin,fujicoin/fujicoin,instagibbs/bitcoin,namecoin/namecoin-core,lateminer/bitcoin,kallewoof/bitcoin,andreaskern/bitcoin,jlopp/statoshi,kallewoof/bitcoin,sipsorcery/bitcoin,fujicoin/fujicoin,tecnovert/particl-core,instagibbs/bitcoin,anditto/bitcoin,fanquake/bitcoin,instagibbs/bitcoin,GroestlCoin/GroestlCoin,GroestlCoin/bitcoin,kallewoof/bitcoin,fujicoin/fujicoin,Xekyo/bitcoin,particl/particl-core,domob1812/bitcoin,Xekyo/bitcoin,Xekyo/bitcoin,dscotese/bitcoin,mruddy/bitcoin,achow101/bitcoin,bitcoinsSG/bitcoin,anditto/bitcoin,dscotese/bitcoin,namecoin/namecore,GroestlCoin/bitcoin,GroestlCoin/GroestlCoin,sipsorcery/bitcoin,GroestlCoin/bitcoin,jambolo/bitcoin,sipsorcery/bitcoin,particl/particl-core,mruddy/bitcoin,kallewoof/bitcoin,namecoin/namecoin-core,Xekyo/bitcoin,namecoin/namecore,mruddy/bitcoin,mruddy/bitcoin,domob1812/bitcoin,jlopp/statoshi,fujicoin/fujicoin,jambolo/bitcoin,dscotese/bitcoin,lateminer/bitcoin,achow101/bitcoin,domob1812/bitcoin,AkioNak/bitcoin,anditto/bitcoin,dscotese/bitcoin,sipsorcery/bitcoin,ajtowns/bitcoin,fanquake/bitcoin,bitcoin/bitcoin,sstone/bitcoin,lateminer/bitcoin,jlopp/statoshi,kallewoof/bitcoin,andreaskern/bitcoin,namecoin/namecoin-core,GroestlCoin/GroestlCoin,jamesob/bitcoin,jlopp/statoshi,jamesob/bitcoin,fanquake/bitcoin,sipsorcery/bitcoin,instagibbs/bitcoin,ajtowns/bitcoin,jambolo/bitcoin,bitcoinsSG/bitcoin,tecnovert/particl-core,GroestlCoin/bitcoin,GroestlCoin/bitcoin,achow101/bitcoin,AkioNak/bitcoin,mruddy/bitcoin,GroestlCoin/GroestlCoin,fujicoin/fujicoin,lateminer/bitcoin,GroestlCoin/bitcoin,domob1812/bitcoin,lateminer/bitcoin,ajtowns/bitcoin,particl/particl-core,AkioNak/bitcoin,namecoin/namecore,anditto/bitcoin,fanquake/bitcoin,Xekyo/bitcoin,tecnovert/particl-core,sipsorcery/bitcoin,fanquake/bitcoin,AkioNak/bitcoin,lateminer/bitcoin,anditto/bitcoin,tecnovert/particl-core,achow101/bitcoin,sstone/bitcoin,Xekyo/bitcoin,jamesob/bitcoin,dscotese/bitcoin