Debug Info: Type Units: Simplify type hashing using IR-provided unique names.

What's good for LTO metadata size problems ought to be good for non-LTO
debug info size too, so let's rely on the same uniqueness in both cases.
If it's insufficient for non-LTO for whatever reason (since we now won't
be uniquing CU-local types or any C types - but these are likely to not
be the most significant contributors to type bloat) we should consider a
frontend solution that'll help both LTO and non-LTO alike, rather than
using DWARF-level DIE-hashing that only helps non-LTO debug info size.

It's also much simpler this way and benefits C++ even more since we can
deduplicate lexically separate definitions of the same C++ type since
they have the same mangled name.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198397 91177308-0d34-0410-b5e6-96231b3b80d8
Revert "Debug Info: Type Units: Simplify type hashing using IR-provided unique names."

Reverting due to bot failure I won't have time to investigate until
tomorrow.

This reverts commit r198397.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198398 91177308-0d34-0410-b5e6-96231b3b80d8