Fix the mtrack memset

src/dog.c

@@ -325,7 +325,7 @@ boolean with_you;
     xyflags = mtmp->mtrack[0].y;
     xlocale = mtmp->mtrack[1].x;
     ylocale = mtmp->mtrack[1].y;
-    memset(mtmp->mtrack, MTSZ, sizeof(coord));
+    memset(mtmp->mtrack, 0, sizeof(mtmp->mtrack));
 
     if (mtmp == u.usteed)
         return; /* don't place steed on the map */

src/monmove.c

@@ -272,7 +272,7 @@ boolean fleemsg;
         mtmp->mflee = 1;
     }
     /* ignore recently-stepped spaces when made to flee */
-    memset(mtmp->mtrack, MTSZ, sizeof(coord));
+    memset(mtmp->mtrack, 0, sizeof(mtmp->mtrack));
 }
 
 STATIC_OVL void

src/teleport.c

@@ -980,7 +980,7 @@ register int x, y;
         }
     }
 
-    memset(mtmp->mtrack, MTSZ, sizeof(coord));
+    memset(mtmp->mtrack, 0, sizeof(mtmp->mtrack));
     place_monster(mtmp, x, y); /* put monster down */
     update_monster_region(mtmp);