One of the claims in #H8849 was that a monster which zapped a wand
that the hero had fully identified made hero's knowledge of it revert
to "a wand". That doesn't happen; it had to have been a different
wand which hadn't been seen up close yet. But the hero should lose
track of known number of charges if a wand is zapped outside his/her
view. When implementing that I noticed that a monster playing a fire
horn to burn away slime was using the routine that gives wand
feedback. Add a separate, similar routine for magical horn feedback.
Half this diff is due to moving a naming support routine from mhitm.c
to do_name.c.
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