* builtins.c (expand_builtin_strcat, expand_builtin_strncat,
	expand_builtin_strspn, expand_builtin_strcspn): New functions.
	(expand_builtin): Handle BUILT_IN_STRCAT, BUILT_IN_STRNCAT,
	BUILT_IN_STRSPN and BUILT_IN_STRCSPN.

	* builtins.def (BUILT_IN_STRCAT, BUILT_IN_STRNCAT,
	BUILT_IN_STRSPN, BUILT_IN_STRCSPN): New entries.

	* c-common.c (c_common_nodes_and_builtins): Declare builtin
	strcat, strncat, strspn and strcspn.
	(string_ftype_string_cstring): Renamed from `string_ftype_ptr_ptr'.

	* extend.texi (strcat, strcspn, strncat, strspn): Document new
	builtins.

testsuite:
	* gcc.c-torture/execute/string-opt-9.c: New test.
	* gcc.c-torture/execute/string-opt-10.c: Likewise.
	* gcc.c-torture/execute/string-opt-11.c: Likewise.
	* gcc.c-torture/execute/string-opt-12.c: Likewise.

From-SVN: r37964