2002.06.23 ~07  FI decoys and count limits

A lot of credit goes to Inferna| on irc://irc.enterthegame.com/#br for
giving me a push in the right direction.

Limiting the number of simultaneous instances of a projectile per player is
now implemented using an array of reference counts.  The actual limit value
is stored with the projectiles definition in the weapons config file.  This
limits some of the insane configurations I've been dreaming up, but for the
most part such restrictions are sensible for what amounts to a WF clone.

The decoy has been solidified.  Now I can stand on my own decoy and shoot
it with just about whatever.  Gauntlet is acting buggy, though.  Currently
the number of deployed decoys isn't limited.  In most MOCK cases, having
more than one decoy doesn't make a whole lot of sense.  Still, I'd like to
mull over whether the coding design for decoys is "good" or not.