DebugInfo: Include default template arguments in template type names

This was committed 4 years ago in 108916 with insufficient testing to
explain why the "getTypeAsWritten" case was appropriate. Experience says
that it isn't - the presence or absence of an explicit instantiation
declaration was causing this code to generate either i<int> or i<int,
int>.

That didn't seem to be a useful distinction, and omitting the template
arguments was destructive to debuggers being able to associate the two
types across translation units or across compilers (GCC, reasonably,
never omitted the arguments).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@205447 91177308-0d34-0410-b5e6-96231b3b80d8
PR19305: Don't issue -Wunused-variable warnings on variable templates. It's not
meaningful to odr-use the VarDecl inside a variable template. (Separately, it'd
be nice to track referenced-ness for templates, and warn on unused ones, but
that's really a distinct issue...)

Move a test that generates and tests a warning-suppressing error out to its own
test file, so it doesn't have weird effects on the other tests in the same file.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@205448 91177308-0d34-0410-b5e6-96231b3b80d8