* diagnostic.c (context_as_prefix): Export.
	(need_error_newline): Remove.
	(lang_diagnostic_starter, lang_diagnostic_finalizer): New objects.
	(error_module_changed, record_last_error_module,
	error_function_changed, record_last_error_function): New functions.
	(initialize_diagnostics): Default intialize
	lang_diagnostic_starter, lang_diagnostic_finalizer.
	(init_output_buffer): Tweak.
	(file_name_as_prefix): New function.
	(announce_function, default_print_error_function,
	report_error_function, set_diagnostic_context): Tweak.

cp/
	* lex.c (lang_init_options): Default diagnostic message maximum
	length to 80, when line-wrapping.

From-SVN: r35836