* rclex.l: add code to suppress certain output from cpp, replace

	* rclex.l: add code to suppress certain output from cpp, replace
	all returns with MAYBE_RETURN
	(MAYBE_RETURN): new, implement the suppression by returning
	IGNORED_TOKEN as needed.
	(cpp_line): remember which file we're in, mark data from included
	*.h files for suppression.
	* rcparse.y (input): allow IGNORED_TOKEN outside of known constructs