Fix for PR7911 and PR7921: make isIntegralOrEnumerationType return false

Fix for PR7911 and PR7921: make isIntegralOrEnumerationType return false
for incomplete enum types.  An incomplete enum can't really be treated as
an "integral or enumeration" type, and the incorrect treatment leads to
bad behavior for many callers.

This makes isIntegralOrEnumerationType equivalent to isIntegerType; I think
we should globally replace the latter with the former; thoughts?

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@111512 91177308-0d34-0410-b5e6-96231b3b80d8