* c-format.c (FMT_FLAG_DOLLAR_GAP_POINTER_OK): New.
	(format_types): Use it for scanf.
	(dollar_arguments_pointer_p): New.
	(init_dollar_format_checking): Store details of which arguments
	are pointers.
	(maybe_read_dollar_number): Reallocate dollar_arguments_pointer_p.
	(finish_dollar_format_checking): Take extra parameter
	pointer_gap_ok.  Treat unused arguments differently if
	pointer_gap_ok and the unused arguments are pointers.
	(check_format_info_main): Pass extra argument to
	finish_dollar_format_checking.
	* doc/invoke.texi (-Wno-format-extra-args): Document behavior when
	unused arguments are present between used arguments with operand
	numbers.

testsuite:
	* gcc.dg/format/strfmon-1.c: Update comments.  Adjust examples
	from Austin Group draft 7.
	* gcc.dg/format/xopen-1.c: Update comments.  Add tests for gaps in
	scanf format arguments.
	* gcc.dg/format/no-exargs-2.c: New test.

From-SVN: r47327