Make the MergeGlobals pass correctly handle the address space qualifiers of the global variables. We partition the set of globals by their address space, and apply the same the trasnformation as before to merge them.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171730 91177308-0d34-0410-b5e6-96231b3b80d8