Fix the problem reported by ais where it was possible for one monster
to knock the hero onto a level teleporter (or trapdoor or hole),
destination was selected and allowed-to-level-teleport checks were made,
then for another monster to knock or teleport the not-yet-relocated-hero
onto the Amulet and have auto-pickup move it into inventory. At the end
of that turn's monster movement, hero would level teleport successfully
despite carrying the Amulet.
This short-circuits monster movement if the hero is scheduled to be
moved to a different level. The monsters who haven't moved yet don't
lose their pending movement points; they'll catch up if/when the hero
returns to the level.
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