opening magic vs holding monster

Zapping wand of opening or spell of knock at engulfer while swallowed
would make the engulfer expel the hero; this change makes zapping
other holders release their hold.  Zapping self now achieves the same
effect, as does breaking a non-empty wand of opening.  When poly'd
hero is holding a monster rather than being held, that monster will
be released.

Engulfers can't re-engulf for 1 or 2 turns after releasing the hero
in order to prevent hero from being immediately re-engulfed.  Impose
the same limitation on other holders.

src/apply.c

@@ -3480,12 +3480,19 @@ do_break_wand(struct obj *obj)
     affects_objects = FALSE;
 
     switch (obj->otyp) {
+    case WAN_OPENING:
+        if (u.ustuck) {
+            release_hold();
+            if (obj->dknown)
+                makeknown(WAN_OPENING);
+            goto discard_broken_wand;
+        }
+        /*FALLTHRU*/
     case WAN_WISHING:
     case WAN_NOTHING:
     case WAN_LOCKING:
     case WAN_PROBING:
     case WAN_ENLIGHTENMENT:
-    case WAN_OPENING:
     case WAN_SECRET_DOOR_DETECTION:
         pline(nothing_else_happens);
         goto discard_broken_wand;
@@ -3502,7 +3509,7 @@ do_break_wand(struct obj *obj)
         dmg *= 2;
         /*FALLTHRU*/
     case WAN_MAGIC_MISSILE:
-    wanexpl:
+ wanexpl:
         explode(u.ux, u.uy, -(obj->otyp), dmg, WAND_CLASS, expltype);
         makeknown(obj->otyp); /* explode describes the effect */
         goto discard_broken_wand;
@@ -3633,7 +3640,7 @@ do_break_wand(struct obj *obj)
     if (obj->otyp == WAN_LIGHT)
         litroom(TRUE, obj); /* only needs to be done once */
 
-discard_broken_wand:
+ discard_broken_wand:
     obj = g.current_wand; /* [see dozap() and destroy_item()] */
     g.current_wand = 0;
     if (obj)