MS ABI: Mangle empty type parameter packs compatibly

The MS mangling scheme apparently has separate manglings for type and
non-type parameter packs when they are empty.  Match template arguments
with parameters during mangling; check the parameter to see if it was
destined to hold type-ish things or nontype-ish things.

Differential Revision: http://reviews.llvm.org/D4792

llvm-svn: 214932