Adjust how LLVM names are produced:

Adjust how LLVM names are produced:
1. Always use % for local and @ for global.
2. Replace NameNeedsQuotes with QuoteNameIfNeeded so that any adjustments
   to the name can be done in one pass.
3. Implement generation of hex escapes so we don't get "wonky" characters
   in the output.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37260 91177308-0d34-0410-b5e6-96231b3b80d8