Remove "localize global" optimization

Summary:
As discussed in http://llvm-reviews.chandlerc.com/D1754,
this optimization isn't really valid for C, and fires too rarely anyway.

Reviewers: rafael, nicholas

Reviewed By: nicholas

CC: rnk, llvm-commits, nicholas

Differential Revision: http://llvm-reviews.chandlerc.com/D1769

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191834 91177308-0d34-0410-b5e6-96231b3b80d8