* NEWS (2.3a+): Mention that -g now takes an argument.

* NEWS (2.3a+): Mention that -g now takes an argument.
* doc/bison.texinfo (Bison Options): Reword -W entry a little for
consistency.  Update the -g and -x entries now that they take
arguments.  Use brackets to indicate optional arguments.
* src/getargs.c (usage): Explain the relationship between arguments of
long and short options more completely.  Document --defines and -d
separately since the former takes an argument but, for POSIX Yacc, the
latter does not.
(short_options): Let -W take an optional argument like --warnings.
(getargs): Sort cases.