Added dump method for global module index.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@206418 91177308-0d34-0410-b5e6-96231b3b80d8
Attempting to unbreak the MSVC 2012 build a second time.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@206420 91177308-0d34-0410-b5e6-96231b3b80d8