Issue reported by elunna: none of the display choices for #terrain
offered a way to show the terrain beneath temporary gas/cloud
regions (except "full map" in wizard mode or explore mode). That
prevented the command from being used to find stairs and portals
which had been mapped before becoming covered up.
Adding extra menu choices to deal with visible regions would result
in #terrain becoming a mess. Instead, treat regions as if they were
traps. Picking a choice that includes traps will show region spots
which are in view as cloud or poison cloud, picking one that excludes
traps will show the underlying terrain. Region spots which aren't
within view are handled the same as before: whatever the hero
remembers at their location gets displayed.
The default menu choice excludes traps so will display stairs that are
covered by gas cloud regions, but not portals, same as when no regions
are present. When showing traps and one is covered by a gas cloud,
the trap will be shown rather than the gas cloud, making it possible
to see known portals.
At the moment the new "#terrain handles regions like traps" feature
hasn't been documented anywhere. That might get rectified someday.
I'm not sure whether trap detection ought to also detect regions now.
This doesn't attempt to tackle that and I think that I'll pretend
that the idea never occurred to me.
'parnoid_confirm:traps' definitely ought to prompt for confirmation
when entering a visible harmful region. This doesn't add that.
Bonus fix: it's possible for a visible region to cover up a not yet
explored location. Searching next to such a spot wasn't changing the
spot to be marked as explored (unless hero was blind). Now it will.
Fixes#1262
b08fb9fb93