Add GDB pretty-printer for llvm::Twine type

Patch by Simon Marchi!

Differential Revision: https://reviews.llvm.org/D30994

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297889 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed