* sysdeps/unix/clock_nanosleep.c (clock_nanosleep): Diagnose EINVAL

* sysdeps/unix/clock_nanosleep.c (clock_nanosleep): Diagnose EINVAL

	for CLOCK_THREAD_CPUTIME_ID, not ENOTSUP.
	Use SYSDEP_NANOSLEEP handler before validating CLOCK_ID value.

	* rt/tst-timer4.c (TEST_CLOCK, TEST_CLOCK_NANOSLEEP): New macros.
	Use them throughout in place of CLOCK_REALTIME and nanosleep.
	(do_test) [TEST_CLOCK_MISSING]: Call this macro and if it returns
	non-null, punt the test with a message using the string returned.
	* rt/tst-timer5.c: New file.
	* rt/Makefile (tests): Add it.