[-cxx-abi microsoft] Mangle TemplateArgument::Declaration for references

Summary:
Properly mangle declarations showing up in template arguments that are
reference parameters.  Fun-fact: undname cannot handle these!

Reviewers: rnk, cdavis5x

Reviewed By: rnk

CC: cfe-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D1356

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@188245 91177308-0d34-0410-b5e6-96231b3b80d8