(effrange, torprange, fortrange): New.

(effrange, torprange, fortrange): New.
(multifire, quiet_bigdef, torp, anti_torp, sd, sb)
(lnd_fort_interdiction, lnd_support, perform_mission, oprange)
(shp_fort_interdiction): Use them.  This fixes forts shooting below
FORTEFF in quiet_bigdef(), lnd_fort_interdiction() and
shp_fort_interdiction().  Change variables for rounded ranges to int.

(quiet_bigdef, sd): Don't scale ship firing range by efficiency.

(dd, sb): Simplify.

(sb): Internal linkage.

(perform_mission): Rename range2 to vrange.