Fix another aspect of PR7047, macro expansions. Previously, this was hacked

Fix another aspect of PR7047, macro expansions. Previously, this was hacked
around by exempting enums from the check, but this doesn't handle a lot of
cases. A better approach is to directly check if the operator comes from
a macro expansion.

I've removed a reference to the rdar that originally led to the enum
suppression when removing it's overly contrived test case. Let me know if that
number or a more reasilistic test case involving enums is still needed.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@108128 91177308-0d34-0410-b5e6-96231b3b80d8