builtins.c (c_strlen): Handle not zero terminated STRING_CSTs correctly.

builtins.c (c_strlen): Handle not zero terminated STRING_CSTs correctly.

	* builtins.c (c_strlen): Handle not zero terminated STRING_CSTs
	correctly.
	* fold-const.c (c_getstr): Fix function comment.  Remove unused third
	argument.  Fix range checks.
	* fold-const.h (c_getstr): Adjust protoype.
	* gimple-fold.c (gimple_fold_builtin_memory_op): Avoid folding when
	string is constant but contains no NUL byte.

From-SVN: r264301