* c-errors.c (pedwarn_c99): Adjust call to report_diagnostic.

	* diagnostic.c (default_diagnostic_starter,
	default_diagnostic_finalizer): New functions.
	(diagnostic_for_asm, diagnostic_for_decl): Tweak.
	(pedwarn, pedwarn_with_file_and_line, error,
	error_with_file_and_line, fatal, warning,
	warning_with_file_and_line): Adjust call to report_diagnostic.
	(report_diagnostic): Rework.
	(set_diagnostic_context): New function.

	* diagnostic.h (struct diagnostic_context): New data structure.
	(diagnostic_message, diagnostic_argument_list,
	diagnostic_file_location, diagnostic_line_location,
	diagnostic_is_warning, diagnostic_starter, diagnostic_finalizer,
	diagnostic_finalizer, diagnostic_auxiliary_data): New macros.
	(set_diagnostic_context): Declare.
	(report_diagnostic): Change prototype.

From-SVN: r35817