* c-common.h (warn_missing_format_attribute): New variable.
	* c-decl.c (warn_missing_format_attribute): New variable.
	(c_decode_option): Decode -Wmissing-format-attribute and
	-Wno-missing-format-attribute.
	* c-common.c (check_function_format): If
	-Wmissing-format-attribute, give a warning where a vprintf or
	vscanf function is called by a function without its own printf or
	scanf attribute.
	* toplev.c (documented_lang_options): Add
	-Wmissing-format-attribute.
	* invoke.texi: Document -Wmissing-format-attribute.

cp:
	* decl2.c (warn_missing_format_attribute): New variable.
	(lang_decode_option): Decode -Wmissing-format-attribute.

testsuite:
	* gcc.dg/format-miss-1.c: New test.

From-SVN: r36897