Thanks to Matt Loper for noticing this behavior.

	* util.c (IDL_parse_filename):
	(IDL_parse_filename_with_input): Call __IDL_parser_reset after
	parse.

	* configure.in: Print a warning if flex isn't installed (one can
	still compile the source distributed flex scanner, however).

	* lexer.l (__IDL_lex_cleanup): Call YY_NEW_FILE.  Because of this
	we now require flex, this is not in standard lex.

	* parser.y (__IDL_parser_reset): New function; call yyclearin.