bag of tricks, horn of plenty, #tip (trunk only)

<Someone> reported that he applied an unID'd bag and it became
discovered as a bag of tricks even though a spellbook appeared on the floor
next to him rather than having a monster show up (the monster was a mimic).
Suppress the bag discovery unless you can see or sense a monster appear.
(This doesn't really achieve much for most players, who'll recognize the
bag because they know that only one type of container doesn't prompt to
take things out and/or put things in, but I think it does make sense.)

     While mucking with bag of tricks I decided that to be consistent with
the behavior of other containers, the #tip command should release all the
monsters in the bag instead of just one.

     And after doing that, I realized that horn of plenty ought to behave
much the same, so #tip will operate on it now.  However, it won't be listed
as a likely candidate in the "which item?" prompt unless/until it has been
discovered.  (Attempting to empty any other type of horn yields "nothing
happens", same as for a horn of plenty with no charges left.)  Emptying a
horn of plenty in a shop can be extremely verbose, but I don't think that
qualifies as a bug and don't currently have any plans to alter it.

doc/fixes35.0

@@ -149,6 +149,7 @@ ensure that the punishment ball and chain make it into the save file after being
 	temporarily orphaned from the normal chains in the swallowing code
 charge for thrown wand that shatters into a thousand pieces in a shop
 wielded light source susceptible to water gets extinguished when weapon rusts
+don't discover unknown bag of tricks when monster it releases is undetected
 
 
 Platform- and/or Interface-Specific Fixes