Improves options in the manual.

	Improves options in the manual.
	* doc/bison.texinfo (-g, -x): Add space before argument.
	(Option Cross Key): Implement FIXME: listing directives also.
	* build-aux/cross-options.pl:  Read from <STDIN> rather than <>.
	(Short Option): Special case -d.  Put arguments inside @option.
	(Bison Directive): Add column, automatically extracted from
	src/scan-gram.l (actual name passed as the first argument)
	with special case for %define.
	* doc/Makefile.am (doc/cross-options.texi): Pass src/scan-gram.l
	to build-aux/cross-options.pl.
	* src/getargs.c (usage): Document limitations of cross-options.pl.
	* src/scan-gram.l: Likewise.