speed of petrified monsters

Someone posted in the newsgroup about using stone-to-flesh
to reanimate a petrified pet and having it come back to life with
boosted speed intact.  When the character gets petrified, stripping
speed is one of the first things which happens, so now do that for
monsters too.  I decided not to make monsters who have normal speed
become slow; there isn't any analogous case for the player.

     Possible bug:  while testing this, I zapped a wand of probing
at a hill orc which had just eaten a lizard corpse to save itself
from stoning.  The feedback said "eating" but the orc immediately
hit and killed me as if it wasn't affected by any movement delay.

src/muse.c

@@ -1,4 +1,4 @@
-/*	SCCS Id: @(#)muse.c	3.4	2002/02/07	*/
+/*	SCCS Id: @(#)muse.c	3.4	2002/08/29	*/
 /*	Copyright (C) 1990 by Ken Arromdee			   */
 /* NetHack may be freely redistributed.  See license for details.  */
 
@@ -2123,6 +2123,10 @@ boolean stoning;
     int nutrit = (obj->otyp == CORPSE) ? dog_nutrition(mon, obj) : 0;
     /* also sets meating */
 
+    /* give a "<mon> is slowing down" message and also remove
+       intrinsic speed (comparable to similar effect on the hero) */
+    mon_adjust_speed(mon, -3, (struct obj *)0);
+
     if (canseemon(mon)) {
 	long save_quan = obj->quan;