fixes "phasing + pits" bugs

fixes completely broken fix from 3.34.2 "update pit trapped time when polymorphing to or from a monster that passes_walls": (fixes C343-17 "After polymorphing into a xorn and returning to human form, player can be stuck in a pit that isn't there." and "Player polymorphed into Xorn is not trapped by pits but (s)he receives "You fall into a pit!" message" and other unreported buggy behaviours)
Smarter warning player before walking into known traps

It is pointless to ask paranoid_trap question for trapped player (there will be no change of position)