mission: Widen coordinate columns to four characters

mission: Widen coordinate columns to four characters

When formatting coordinates for fixed-width output, the width should
be at least four characters.

Columns x,y and op-sect use three.  Has always been that way.  Widen
them both to four.  This cleans up output for world sizes between 200
and 1998.

Signed-off-by: Markus Armbruster <armbru@pond.sub.org>