shattering monster's weapon stack

Something I encountered while playing slash'em a while back, but
relevant to nethack:  "Its orcish spears shatter from the force of your
blow!".  I was using a two-handed weapon (at skilled or expert level) to
fight an invisible monster which was wielding a stack of multiple spears
(slash'em gives them out in groups of 3 for monsters' starting inventory).
After killing it, I found 2 orcish spears along with an invisible corpse
of somebody-or-other the Kobold King.  The message suggested that the
whole spear stack had been destroyed (and the weapon shattering code in
hmon_hitmon() clearly expects that to be the case), but only one of them
had actually gotten used up.

     I can't recall whether "shatter" was actually given as singular or
plural at the time; nethack handles that aspect correctly.  Only object
destruction needed tweaking.

doc/fixes34.4

@@ -203,6 +203,7 @@ handle antholes more sensibly when ants aren't available
 cancelled nurses shouldn't say "Relax, this won't hurt a bit"
 check for hero location in digactualhole() before clearing u.utrap
 clear any pits that the hero digs in the vault guard's temporary corridor
+shattering a monster's weapon didn't work as intended for stack of N>1
 
 
 Platform- and/or Interface-Specific Fixes