auto fill comments

[<dove at MIT-TWEETY-PIE>]

In zwei in Release 5.0 [Beta Test rev 7], on Lisp Machine Tweety Pie (3600):

It turns out, that due to the workings of fill long comment, if ALL
lines in the comment containing ";;" have at least one space after the
semi's (i.e. even "blank" lines have a space after the semi's) then fill
long comment will leave space between the semi's and the text.  One can
either leave "blank" lines totally blank (i.e. no semi's) or put a space
after them.

This is because fill long comment looks for the shortest comment prefix
in the long comment, and uses that as the fill prefix.

It would be nice it would (perhaps optionally) insert a space after the
semi's when the fill prefix turns out to be just semi's, so it would be
compatible with auto fill lisp comment mode.