Update for llvm change.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@219952 91177308-0d34-0410-b5e6-96231b3b80d8
No longer emit diagnostics about unused results (comparisons, etc) from unevaluated contexts. Fixes PR18571.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@219954 91177308-0d34-0410-b5e6-96231b3b80d8