MS ABI: Add support for the -vm{b,g,s,m,v} flags

These flags control the inheritance model initially used by the
translation unit.

Differential Revision: http://llvm-reviews.chandlerc.com/D2741


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@201175 91177308-0d34-0410-b5e6-96231b3b80d8