This takes care of a number of bugs / inconsistencies:
* Ships with zero firing range could return fire and fire support, but
not fire actively or interdict. Fix by testing for gun limit
instead in multifire() and mission(). No ships in the stock game
are affected.
* Required gun crew was inconsistent: multifire() let N military fire
max(1,floor(N/2)) guns for active fire. Ditto perform_mission() for
interdiction. quiet_bigdef() let them fire N guns for returning gun
fire. Ditto sd() for firing support and firing at boarding parties.
fire_dchrg() let them fire floor(N/2) for returning fire to
torpedoes. Unify to let N military fire floor((N+1)/2) guns.
* Shell use was inconsistent: sd() and perform_mission() used one
shell per gun, everything else one per two guns. Unify to one shell
per two guns.
* Shell resupply bugs: multifire() got two shells regardless of actual
ammo use. quiet_bigdef() got one shell (but use_ammo() uses only
one, which is a bug). sd() and perform_mission() resupplied before
checking all other requirements and could thus get more shells than
actually needed.
Markus Armbruster
22c6fd8bf6