Further fixes to the tcltk interface

[Hans Ronne <hronne at telia dot com>]

Some recent improvements to the tcltk interface:

Unit and feature names are now scaled when you change the resolution.
Feature names are drawn using a larger font, except for single cell
features (peaks etc) which are drawn using the same font as for unit names.

The world map has been fixed so that the map outline box always is updated
correctly and never leaves any garbage behind when you scroll the world map
itself.

The big map no longer jumps into the upper left corner and then back again
into the center when you zoom it (this may seem like an easy thing to fix
but it was one of the hardest bugs in the tcltk interface so far).

Hans