- Fire delrecord events when items are discard()ed from a set-backed   InstrumentedList, just like remove().
- Fire delrecord events when items are discard()ed from a set-backed
  InstrumentedList, just like remove().

hsum/sqlalchemy,Akrog/sqlalchemy,276361270/sqlalchemy,alex/sqlalchemy,monetate/sqlalchemy,zzzeek/sqlalchemy,WinterNis/sqlalchemy,brianv0/sqlalchemy,Cito/sqlalchemy,Cito/sqlalchemy,olemis/sqlalchemy,sqlalchemy/sqlalchemy,davidjb/sqlalchemy,davidfraser/sqlalchemy,elelianghh/sqlalchemy,dstufft/sqlalchemy,brianv0/sqlalchemy,inspirehep/sqlalchemy,inspirehep/sqlalchemy,pdufour/sqlalchemy,alex/sqlalchemy,dstufft/sqlalchemy,davidfraser/sqlalchemy,epa/sqlalchemy,EvaSDK/sqlalchemy,halfcrazy/sqlalchemy,wujuguang/sqlalchemy,bootandy/sqlalchemy,WinterNis/sqlalchemy,bdupharm/sqlalchemy,elelianghh/sqlalchemy,wujuguang/sqlalchemy,monetate/sqlalchemy,sandan/sqlalchemy,pdufour/sqlalchemy,wfxiang08/sqlalchemy,graingert/sqlalchemy,Akrog/sqlalchemy,bootandy/sqlalchemy,EvaSDK/sqlalchemy,itkovian/sqlalchemy,itkovian/sqlalchemy,epa/sqlalchemy,ThiefMaster/sqlalchemy,olemis/sqlalchemy,halfcrazy/sqlalchemy,j5int/sqlalchemy,ThiefMaster/sqlalchemy,robin900/sqlalchemy,j5int/sqlalchemy,sandan/sqlalchemy,hsum/sqlalchemy,Cito/sqlalchemy,276361270/sqlalchemy,wfxiang08/sqlalchemy,bdupharm/sqlalchemy,davidjb/sqlalchemy,graingert/sqlalchemy,alex/sqlalchemy,robin900/sqlalchemy