Suffixing #pragma comment(lib) library names with .lib if necessary.  This matches MSVC behavior, as well as allows us to properly link libraries such as the ones provided by the MSDN examples.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182647 91177308-0d34-0410-b5e6-96231b3b80d8