Don't compare native_handle_t against 0 --- do appropriate checks in create_native_thread for platforms where pthread_t is not comparable

[SVN r41396]

libs/thread

@@ -1 +1 @@
-Subproject commit 5ded171247340446b95975d229341f451dd8111e
+Subproject commit 270e88edd7fe2d4f7edeef5686c32d6b3e794071