Fix a DSA bug that caused DSA to generate incredibly huge graphs and take forever to

Fix a DSA bug that caused DSA to generate incredibly huge graphs and take forever to
do it on povray.  The problem is that we were not copying globals from callees to
callers unless the existed in both graphs.  We should have copied them in the case
where the global pointed to a node that was copied as well.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12104 91177308-0d34-0410-b5e6-96231b3b80d8