Add sysconf BONES_POOLS to allow more bones-files per level

Reduce the chance of a player playing on a public server encountering
their own bones, by implementing separate bones pools. The pool a player
belongs to is determined at game start, and only bones in that pool
are used. The sysconf BONES_POOLS allows the sysadmin to define how
many pools there are.

src/sys.c

@@ -40,6 +40,7 @@ sys_early_init()
     sysopt.explorers = (char *) 0;
     sysopt.genericusers = (char *) 0;
     sysopt.maxplayers = 0; /* XXX eventually replace MAX_NR_OF_PLAYERS */
+    sysopt.bones_pools = 0;
 
     /* record file */
     sysopt.persmax = PERSMAX;