Reland r200340 - 'Add line table debug info to COFF files when using a win32 triple'

This incorporates a couple of fixes reviewed at http://llvm-reviews.chandlerc.com/D2651

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200440 91177308-0d34-0410-b5e6-96231b3b80d8