* thread.c (thread_id_make_value): Make a value representing the

	* thread.c (thread_id_make_value): Make a value representing the
	current thread.
	(_initialize_thread): Create $_thread.

	* gdb.texinfo (Debugging Programs with Multiple Threads): Describe
	$_thread.

	* gdb.threads/thread-specific.exp: Add tests of $_thread.