Add -std=gnu11 and -std=c11 NPTL initializers tests.

Add -std=gnu11 and -std=c11 NPTL initializers tests.

NPTL has tests that initializers work with various -std= options.  Now
that we can rely on -std=gnu11 and -std=c11 being available, this
patch adds versions of those tests for those options.

Tested for x86_64 and x86 (testsuite).

	* nptl/tst-initializers1-c11.c: New file.
	* nptl/tst-initializers1-gnu11.c: Likewise.
	* nptl/Makefile (tests): Add these new tests.
	(CFLAGS-tst-initializers1-c11.c): New variable.
	(CFLAGS-tst-initializers1-gnu11.c): Likewise.