New Xconq features in CVS

[Stan Shebs <shebs at shebs dot cnchost dot com>]

I've just checked in another small pile of changes:

1) The AI now has a rudimentary knowledge of how to
collect materials that are needed for construction
of units.  You can see this in action in ancients.g.
Not very good yet, it still can't do two levels of
indirection "get wood to build barracks to build
warriors", and it also doesn't know how to balance
collecting vs exploring very well.

2) Mud and snow are available to games that have
varying temperatures, plus coating display is
implmented in the tcl/tk interface, so now you
can watch General Winter advance and retreat each
year in ww2-eur-42.g.  Mud and snow both cost extra
to move through, so now an offensive can be stalled
by bad weather.  The weather computations seem to
have a bug still, since Russia gets quite a lot of
snow in October, which doesn't look quite right...

Stan