rework the ex parser to pass around lengths instead of nul terminated

rework the ex parser to pass around lengths instead of nul terminated
strings, and to use ARGS *[], not char *[]'s for argument passing
major parser reorganization so that the termcap reorder script would
work.  The underlying problem was that you can't look past addresses
to figure out how long commands are, so you have to do it all inline,
left to right.