This helper function needs the type identifier map when we switch
DIType::getContext to return DIScopeRef instead of DIScope.
Since isSubprogramContext is used by DwarfDebug only, We move it to DwarfDebug
to have easy access to the map.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190325 91177308-0d34-0410-b5e6-96231b3b80d8