[freeciv-ai] coreai: process_defender_want()

["Per I. Mathisen" <per@xxxxxxxxxxx>]

Very few changes. The only important ones:
 - Now also considers air and helicopter units as defenders. Since the
previous fix to unit_desirability() reduces the want for helis and few
aircraft are worth building as defenders (none) anyway, this won't have
much effect.
 - F_FIELDUNIT can now be built as defenders. There is no reason why this
should be impossible, only reduce the weight for it to represent the risk
(increased unhappiness). The comment preceding this conditional was wrong
about the effects of the flag as well.
 - I did NOT make the want for a tech depend on how many steps we would
have to take to get there, as Ross had done. This is the wrong place to do
this. The tech code should factor this in.
 - I did NOT make the default defender into an illegal value, and I
removed the comment which said that having unittype zero (settlers) as
default was a bug. It is not.

Yours
Per

coreai4.diff
Description: Text document