[clang] Do not traverse EnumDecl's type in RecursiveASTVisitor
This is inconsistent with the code and comments in
RecursiveASTVisitor.h and is not a correct behavior:
We shouldn't traverse D->getTypeForDecl(); it's a result of
declaring the type, not something that was written in the source.
Fixes the failures in 1c2e249f938c50e1b331a1f7adc83c0a381f3897