PR14492: Debug Info: Support for values of non-integer non-type template parameters.

This is only tested for global variables at the moment (& includes tests
for the unnamed parameter case, since apparently this entire function
was completely untested previously)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181632 91177308-0d34-0410-b5e6-96231b3b80d8