Freeciv

I added "Capturable" flag to some transport ships, and now they can be captured by land unit
(either if close to the shore, or from aboard if land unit class have non-native flags on).
Noteworthy is, that after successful capture, land units doesn't enter aboard captured ship.

Unfortunately, it works well only for empty transport ships. If ship is loaded, it cause server crash with the following message:

1: in create_unit_full() [../../../../server/unittools.c::1581]: assertion '!ptile || can_unit_exist_at_tile(punit, ptile)' failed.

I checked also case with capturing land units, which can carry other units: whole stack is captured.
Maybe it is a bug - loaded unit should not to be captured, as stacked units are.