More xconq bug fixes

[Hans Ronne]

I checked in a couple of new bug fixes yesterday. One bug (just a typo, but
a significant one) would cause acp-independent units to build nothing but
siege units. Hence the myriads of catapults in the Third Age game.

Another bug in the kernel code for occupant-transport volume checks would
cause crashes in the build code. It dealt with the rather unusual (but
still possible) situation where a unit builds another unit around itself,
perhaps this is why it escaped detection until now.

Hans

Hans Ronne

hronne@pp.sbbs.se