Two more AI bugs

[Lincoln Peters <peters2000 at mindspring dot com>]

I noticed a fairly serious problem when the AI tries to play
"Colonizer".  I defined spaceports and cities as different units,
thinking that a spaceport would be able to build air units (motherships,
saucers, and fighters), while all the city types could build everything
else.  However, the AI seems to be telling spaceports to build non-air
units, such as infantry and armor, and as a result, the spaceports
idle.  I don't see that problem in any other games (although I don't
think that any other game uses different advanced units that don't all
build the same units). 

I also noticed that when under AI control, floating cities move around
quite a bit, but they never seem to build any units.  It doesn't seem
like they're trying to build the wrong units (all cities work fine as
producers under AI control); but rather they're being used exclusively
as gigantic troop transports.  Perhaps the AI can't understand all of
the functions of the floating city?  I see that it has the same problem
with tribes in "roman" (and probably also with flying cities in "time").