* builtins.c (unterminated_array): Add new arguments.
	If argument is not terminated, bubble up size and exact
	state to callers.
	(expand_builtin_strnlen): Detect, avoid expanding
	and diagnose unterminated arrays.
	(c_strlen): Fill in offset of start of unterminated strings.
	* builtins.h (unterminated_array): Update prototype.

	* gcc.dg/warn-strnlen-no-nul.c: New.

Co-Authored-By: Jeff Law <law@redhat.com>

From-SVN: r264787