* gcov.c (source_prefix, source_length): New globals.
	(flag_relative_only): Likewise.
	(print_usage, options, process_args): Update.
	(generate_results): Use coverage.name, check
	flag_relative_only. Adjust messages.
	(find_source): Check source_prefix.
	(output_lines): Use coverage.name, adjust messages.
	* doc/gcov.texi (Invoking Gcov): Document new options.

From-SVN: r181335