Added support for global memory reference lookup.
Added support for global memory reference lookup.

chubbymaggie/angr,angr/angr,xurantju/angr,angr/angr,tyb0807/angr,cureHsu/angr,haylesr/angr,avain/angr,chubbymaggie/angr,angr/angr,tyb0807/angr,zhuyue1314/angr,fjferrer/angr,f-prettyland/angr,iamahuman/angr,mingderwang/angr,avain/angr,schieb/angr,haylesr/angr,GuardianRG/angr,axt/angr,axt/angr,fjferrer/angr,terry2012/angr,chubbymaggie/angr,tyb0807/angr,terry2012/angr,lowks/angr,zhuyue1314/angr,axt/angr,mingderwang/angr,f-prettyland/angr,lowks/angr,GuardianRG/angr,cureHsu/angr,f-prettyland/angr,iamahuman/angr,xurantju/angr,schieb/angr,iamahuman/angr,schieb/angr