fix issue #872 - container-to-container #tip

Reported by k2:  tipping one container's contents directly into
another container allowed transferring a wand of cancellation (not
mentioned:  or a bag of holding or a bag of tricks) into a bag of
holding without blowing it up.

That's now fixed.  There are other issues that this doesn't touch:

I think it's odd that you can transfer stuff from one carried
container to another but not from a carried container to a floor
container nor from one floor container to another one at same spot.

I didn't test shop billing so an not sure what happens when #tip
blows up a bag of holding and there are some unpaid items involved.

Using #tip on horn of plenty treats it like a container, but doing
that when it's carried doesn't offer the chance to tip its contents
directly into a carried container.

Tipping a carried container does not require free hands or even
limbs (for playability) but tipping such into another container
should require at least one free hand.

Fixes #872

src/apply.c

@@ -4006,7 +4006,7 @@ doapply(void)
     case SACK:
     case BAG_OF_HOLDING:
     case OILSKIN_SACK:
-        res = use_container(&obj, 1, FALSE);
+        res = use_container(&obj, TRUE, FALSE);
         break;
     case BAG_OF_TRICKS:
         (void) bagotricks(obj, FALSE, (int *) 0);