nptl: Convert tst-sem5 & tst-sem13 to use libsupport

Checked on x86_64-linux-gnu and i686-linux-gnu.

	* nptl/tst-sem5.c: Remove unused headers. Add <support/check.h>.
	(do_test) Use libsupport test macros rather than hand-coded
	conditionals and error messages. Ensure that sem_init returns zero
	rather than not -1. Use <support/test-driver.c> rather than
	test-skeleton.c.

	* nptl/tst-sem13.c: Add <support/check.h>. (do_test) Use libsupport
	test macros rather than hand-coded conditionals and error messages.
	Use <support/test-driver.c> rather than test-skeleton.c.