The code trying to assign a typedef to an anonymous tag declaration was

The code trying to assign a typedef to an anonymous tag declaration was
extremely rambunctious, both on parsing and on template instantiation.
Calm it down, fixing an internal consistency assert on anonymous enum
instantiation manglings.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@124653 91177308-0d34-0410-b5e6-96231b3b80d8