Rework recursive_timed_mutex so that it uses __thread_id instead of using the lower-level __libcpp_thread_id. This is prep for fixing PR42918. Reviewed as https://reviews.llvm.org/D65895

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@368867 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed