C++11 is required, remove some preprocessor checks for it

We require C++11 to build, so remove a few remaining preprocessor checks for
'__cplusplus >= 201103L'. This should always be true.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@264572 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed