Remove 'not' from some CodeGen tests

These were just missing an expected-no-diagnostics directive.

Also add -std=c++11 to a test warning noisly about extensions.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@197308 91177308-0d34-0410-b5e6-96231b3b80d8