Various Windows SDK headers use _MSC_VER values to figure out what
version of the VC++ headers they're using, in particular for SAL macros.
Patch by Paul Hampson!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191015 91177308-0d34-0410-b5e6-96231b3b80d8