Mark C++14 status as 'complete'

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@205504 91177308-0d34-0410-b5e6-96231b3b80d8
Reword C++14 status to match C++11 status


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@205505 91177308-0d34-0410-b5e6-96231b3b80d8