This patch reverses the edge from DIGlobalVariable to GlobalVariable.
This will allow us to more easily preserve debug info metadata when
manipulating global variables.
Fixes PR30362. A program for upgrading test cases is attached to that
bug.
Differential Revision: http://reviews.llvm.org/D20147
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@281284 91177308-0d34-0410-b5e6-96231b3b80d8