Fix suggestions for non-trivial Wformat type cases (PR c/72858)

Fix suggestions for non-trivial Wformat type cases (PR c/72858)

gcc/c-family/ChangeLog:
	PR c/72858
	* c-format.c (argument_parser::check_argument_type): Add params
	"type_start" and "conversion_char".  Use the former to generate
	offset_to_type_start and pass it and conversion_char to
	check_format_types.
	(check_format_info_main): Capture the start of the type
	information as "type_start", and pass it an format_char
	to arg_parser.check_argument_type.
	(check_format_types): Provide an example in the leading comment.
	Add params "offset_to_type_start" and "conversion_char"; pass
	them to format_type_warning calls.
	(test_get_modifier_for_format_len): Likewise.
	(matching_type_p): New function.
	(get_format_for_type): Add param "conversion_char" and move
	implementation into...
	(get_format_for_type_1): ...new function, called twice.
	Use new function matching_type_p rather than checking for
	TYPE_CANONICAL equality.
	(get_corrected_substring): New function.
	(format_type_warning): Provide an example in the leading comment.
	Add params "offset_to_type_start" and "conversion_char".  Replace
	call to get_format_for_type with call to get_corrected_substring
	and move rejection of hints for widths/precisions there.
	(assert_format_for_type_streq): Add param "conversion_char".
	(ASSERT_FORMAT_FOR_TYPE_STREQ): Add param CONVERSION_CHAR.
	(test_get_format_for_type_printf): Add conversion chars to the
	tests, adding coverage for various combinations of integer
	vs double conversions, and for preserving octal and hexadecimal
	conversions.
	(test_get_format_for_type_scanf): Add conversion chars to the
	tests.

gcc/testsuite/ChangeLog:
	PR c/72858
	* gcc.dg/format/diagnostic-ranges.c: Update expected suggestions
	to preserve conversion chars, and to preserve prefix information.
	* gcc.dg/format/pr72858.c: New test case.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@240095 138bc75d-0d04-0410-961f-82ee72b054a4