Add WinLinkDriver and connect it to the existing COFF reader. Remaining
parts are still stubs, so while it can now read a COFF file, it still
cannot link or output PE/COFF files yet.
Reviewers: Bigcheese
CC: llvm-commits
Differential Revision: http://llvm-reviews.chandlerc.com/D865
llvm-svn: 182784
