[UPSTREAM][DebugInfo] Emit DW_TAG_enumeration_type for referenced global enumerator.

This essentially reverts changes from r361400 while keeping behavior for
CodeView.

Reviewers: akhuang, rnk, probinson

Reviewed by: rnk

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D67141



llvm-svn: 370981
(cherry picked from commit 48c6fadc)
Bug: 141288540
Change-Id: I337d80b3c9936e123399848e24147d8d4af78939
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>