substring-locations: add class format_string_diagnostic_t

substring-locations: add class format_string_diagnostic_t

With the addition of ranges in r263564, format_warning_at_substring_n
has 10 arguments.

Reduce the number of args by bundling the shared ones into a
class format_string_diagnostic_t.

gcc/c-family/ChangeLog:
	* c-format.c (format_warning_at_char): Update for introduction of
	format_string_diagnostic_t.
	(format_type_warning): Likewise.

gcc/ChangeLog:
	* gimple-ssa-sprintf.c (fmtwarn): Update for introduction of
	format_string_diagnostic_t.
	(fmtwarn_n): Likewise.
	* substring-locations.c
	(format_string_diagnostic_t::format_string_diagnostic_t) New ctor.
	(format_warning_n_va): Convert to...
	(format_string_diagnostic_t::emit_warning_n_va): ...this.
	(format_warning_va): Convert to...
	(format_string_diagnostic_t::emit_warning_va): ...this.
	(format_warning_at_substring): Convert to...
	(format_string_diagnostic_t::emit_warning): ...this.
	(format_warning_at_substring_n): Convert to...
	(format_string_diagnostic_t::emit_warning_n): ...this.
	* substring-locations.h (class format_string_diagnostic_t): New
	class.
	(format_warning_va): Convert to
	format_string_diagnostic_t::emit_warning_va.
	(format_warning_n_va): Convert to
	format_string_diagnostic_t::emit_warning_n_va.
	(format_warning_at_substring): Convert to
	format_string_diagnostic_t::emit_warning.
	(format_warning_at_substring_n): Convert to
	format_string_diagnostic_t::emit_warning_n.

From-SVN: r264372