Patch to allow different city radiuses.

 Marko Lindqvist <caz@cc.tut.fi>


 This patch adds new server option 'cityradius'. It controls size of the area,
where city can send it's workers.


 Some notes:

 - Originally made against freeciv CVS version fetched 03.Jan.00.
   Looking freeciv ChageLog I don't see any reason to believe it's broken yet
   (06.Jan.00).
 - Don't know how well AI handles this, I hope that I undestood (and changed)
   at least minimap handling right.
 - Gtk and Xaw clients should work all right, Mui client is not patched.
 - If either server or is able to handle different city radiuses
   (this patch installed), other one(s) have to be too. This applies even when
   playing with default (2) city radius. 
 - I haven't tested too much. I have probably missed some places where radius
   is hard coded. Hopefully I have not changed any hardcoded values which
   actually have nothing to do with city radius, but at first glance
   looked like they do.
 - I didn't change max value for server option unhappysize, though
   6 is still a bit low for cities with radius '3'.
 - Clients do not (yet?) show value of the cityradius.
 - If you change your city radius, remember to consider other options
   accordingly. I seriously doubt anybody wants to play with city radius '1',
   but with city radius '3' you might want to consider following changes to
   your settings used with default city radius:
   - Lower 'specials' (less within city area)
   - Lower 'foodbox'  (city grows faster -> use for extra area)
     You might then want to balance faster growing by:
     - Increase 'researchspeed' (lowers researchspeed :)
     - Increase building costs at buildings.ruleset and units.ruleset.
     - Make terrains less valuable at terrain.ruleset
     - Increase 'aqueduct_size' and 'sewer_size' at buildings.ruleset.
   - Increase 'xsize' and 'ysize'
   - Increase 'landmass' (It can be painfull to try optimally set these
                          big cities to small island)    
   - Increase 'unhappysize' (so cities won't start revolting when thay are
                             hardly built)
   - Lower 'cityfactor' (You are going to have less cities)
   - Lower 'civilwarsize' ( --''-- )