message: disable HAVE_THREAD_LOCAL on unreliable platforms
  Note that this doesn't affect anything unless
  DEBUG_LOCKCONTENTION is defined.
  See discussions here:
diff: @@ -827,8 +827,23 @@ AC_LINK_IFELSE([AC_LANG_SOURCE([
  }
  ])],
  [
  + case $host in
  + *mingw*)
  + # mingw32's implementation of thread_local has also been shown to behave
  + # erroneously under concurrent usage; see:
  + # https://gist.github.com/jamesob/fe9a872051a88b2025b1aa37bfa98605
  + AC_MSG_RESULT(no)
  + ;;
  + *darwin*)
  + # TODO enable thread_local on later versions of Darwin where it is
  + # supported (per https://stackoverflow.com/a/29929949)
  + AC_MSG_RESULT(no)
  + ;;
  + *)
  AC_DEFINE(HAVE_THREAD_LOCAL,1,[Define if thread_local is supported.])
  AC_MSG_RESULT(yes)
  + ;;
  + esac
  ],
  [
  AC_MSG_RESULT(no)
  