Implement DDG.data_sub_graph().
Implement DDG.data_sub_graph().

angr/angr,f-prettyland/angr,schieb/angr,iamahuman/angr,tyb0807/angr,chubbymaggie/angr,schieb/angr,iamahuman/angr,f-prettyland/angr,tyb0807/angr,schieb/angr,axt/angr,axt/angr,chubbymaggie/angr,f-prettyland/angr,axt/angr,angr/angr,tyb0807/angr,angr/angr,iamahuman/angr,chubbymaggie/angr