Simplify format_warning_at_substring API

Simplify format_warning_at_substring API

The format_warning_at_substring API has a rather clunk way of indicating
the location of the pertinent param (if any): a source_range * is passed
in, which can be NULL.  Doing so requires extracting a range from the
location_t and passing around a pointer to it, or NULL, as needed.

This patch simplifies things by eliminating the source_range * in
favor of a location_t, with UNKNOWN_LOCATION used to signify that
no param location is available.

gcc/c-family/ChangeLog:
	* c-format.c (format_warning_at_char): Pass UNKNOWN_LOCATION
	rather than NULL to format_warning_va.
	(check_format_types): Likewise when calling format_type_warning.
	Remove code to extract source_ranges and source_range * in favor
	of just a location_t.
	(format_type_warning): Convert source_range * param to a
	location_t.

gcc/ChangeLog:
	* gimple-ssa-sprintf.c (fmtwarn): Update for changed signature of
	format_warning_at_substring.
	(maybe_warn): Convert source_range * param to a location_t.  Pass
	UNKNOWN_LOCATION rather than NULL to fmtwarn.
	(format_directive): Remove code to extract source_ranges and
	source_range * in favor of just a location_t.
	(parse_directive): Pass UNKNOWN_LOCATION rather than NULL to
	fmtwarn.
	* substring-locations.c (format_warning_va): Convert
	source_range * param to a location_t.
	(format_warning_at_substring): Likewise.
	* substring-locations.h (format_warning_va): Likewise.
	(format_warning_at_substring): Likewise.

From-SVN: r253827