c-format.c (init_function_format_info): Check __builtin_printf and __builtin_fprintf even if -ffreestanding.

	* c-format.c (init_function_format_info): Check __builtin_printf
	and __builtin_fprintf even if -ffreestanding.  Check C99 functions
	in gnu89 mode.

testsuite:
	* gcc.dg/format/builtin-1.c, gcc.dg/format/ext-6.c: New tests.

From-SVN: r45757