* builtins.def (BUILT_IN_STPNCPY, BUILT_IN_STRCASECMP,
	BUILT_IN_STRNCASECMP): New.
	* doc/extend.texi: Document stpncpy, strcasecmp, strncasecmp
	and strndup.

testsuite:
	* gcc.dg/nonnull-3.c: Also test __builtin_stpncpy,
	__builtin_strcasecmp and __builtin_strncasecmp.

From-SVN: r97498