(CR) Buffs the siege crossbow

Re http://smf.cataclysmdda.com/index.php?topic=14.msg174847#msg174847

Still nontrivial amounts of recoil & dispersion, but at high skill you can now one-shot zeds using metal bolts.  Would be interested in thoughts on how to make this worthwhile under the new aiming system (or that it won't be worthwhile, and should be considered a museum piece).