Attempt to reapply this patch for caching copy assignment operator
lookup. Previously, it was breaking self-host, but it's been a week and
a half and I can't reproduce, so I need to see if it's still failing.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@133581 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed