* builtins.c (c_strlen): Add only_value argument.
	Handle COND_EXPR and COMPOUND_EXPR.
	(expand_builtin_strlen): Optimize also strlen (i++ ? "foo" : "bar").
	Adjust c_strlen callers.
	(expand_builtin_strcpy, expand_builtin_strncpy,
	expand_builtin_strcmp, expand_builtin_strncmp,
	expand_builtin_fputs, expand_builtin_sprintf,
	fold_builtin): Adjust c_strlen callers.

	* gcc.c-torture/execute/builtins/string-8.c: New test.
	* gcc.c-torture/execute/builtins/string-8-lib.c: New.
	* gcc.c-torture/execute/stdio-opt-1.c (main): Add new tests.
	* gcc.c-torture/execute/string-opt-7.c (main): Add new test.

From-SVN: r68634