slightly simplify/optimize string/unicode bind processor
slightly simplify/optimize string/unicode bind processor

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