[-cxx-abi microsoft] Mangle __uuidof correctly into template parameters

[-cxx-abi microsoft] Mangle __uuidof correctly into template parameters

Summary:
It seems that __uuidof introduces a global extern "C" declaration of
type __s_GUID.  However, our implementation of __uuidof does not provide
such a declaration and thus must open-code the mangling for __uuidof in
template parameters.

This allows us to codegen scoped COM pointers and other such things.

This fixes PR16836.
Depends on D1356.

Reviewers: rnk, cdavis5x, rsmith

Reviewed By: rnk

CC: cfe-commits
Differential Revision: http://llvm-reviews.chandlerc.com/D1357

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@188252 91177308-0d34-0410-b5e6-96231b3b80d8