still more Master Key of Thievery

Make #untrap while carrying the non-cursed (for rogues) or blessed
(for non-rogues) Key work the same as #invoke has been doing (without
regard to its bless/curse state):  when used on trapped door or chest,
that trap will always be found and disarming it will always succeed.

It should work when carried by monsters too:  if they try to open a
trapped door while carrying the Key (must be blessed since they're
not rogues) the trap will be automatically disarmed.  (Caveat:  that
hasn't been adequately tested.)

TODO (maybe...):  change the #invoke property to detect unseen/secret
door detection instead of #untrap.  The latter isn't completely
redundant; it works when the Key is cursed.  But quest artifacts
strongly resist becoming cursed so that isn't a particularly useful
distinction.

Also, trap hints when wielding the Key without gloves didn't notice
adjacent door and chest traps.  Now it does.  And the behavior is
slightly different:  known traps covered by objects or monsters are
treated like unknown traps as far as the hot/cold hints go.

src/trap.c

@@ -4256,6 +4256,11 @@ boolean force;
         pline_The("perils lurking there are beyond your grasp.");
         return 0;
     }
+    /* 'force' is true for #invoke; make it be true for #untrap if
+       carrying MKoT */
+    if (!force && has_magic_key(&youmonst))
+        force = TRUE;
+
     ttmp = t_at(x, y);
     if (ttmp && !ttmp->tseen)
         ttmp = 0;