Have a single way for creating unique value names.

Have a single way for creating unique value names.

We had two code paths. One would create names like "foo.1" and the other
names like "foo1".

For globals it is important to use "foo.1" to help C++ name demangling.
For locals there is no strong reason to go one way or the other so I
kept the most common mangling (foo1).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@253804 91177308-0d34-0410-b5e6-96231b3b80d8