conformtest: Correct some limits.h expectations for XPG3, XPG4.

The conform/ test of limits.h namespace for XPG3 was failing because
of NL_* and NZERO defines.  Those symbols are EX-shaded, not
UX-shaded, so it's correct for them to be defined for XPG3; this patch
corrects the expectations accordingly.  (Actually it looks like they
should not be listed as optional for these standards, but that's
another matter.)

Tested for x86_64 and x86.

	* conform/data/limits.h-data (CHARCLASS_NAME_MAX): Also expect for
	[XPG3 || XPG4].
	(NL_ARGMAX): Also expect for [XPG3].
	(NL_LANGMAX): Likewise.
	(NL_MSGMAX): Likewise.
	(NL_NMAX): Likewise.
	(NL_SETMAX): Likewise.
	(NL_TEXTMAX): Likewise.
	(NZERO): Likewise.
	(TMP_MAX): Likewise.
	* conform/Makefile (test-xfail-XPG3/limits.h/conform): Remove
	variable.