Add a test for positional parameters in g_snprintf(). Use g_printf()

Add a test for positional parameters in g_snprintf(). Use g_printf()

	* tests/string-test.c: Add a test for positional parameters in
	g_snprintf().
	* glib-genmarshal.c, gobject-query.c: Use g_printf() instead of
	system printf.  (#99319)