core dump in drawing names

[Hans Ronne]

>Here's a core dump (I got it by restoring a certain saved game and
>hitting "{" twice) in drawing names.  The cause of the core dump was
>that a negative value for the x coordinate was being pased to
>draw_units (with the core dump in unit_view_at).
>
>The enclosed patch does prevent the core dump but I'm not sure it is
>quite right, especially in the case of cylindrical worlds.

I'll look into this. I just ported this code from the macppc interface
(where it works fine) to the tcltk interface.

Hans