Let Powered by Death work with all corpses

...including "mangled" (formerly NO_HIDE) corpses from Kiku.

The interaction is and was invisible and counterintuitive, and
the bulk of it was inadvertently broken by 54438205d933 anyway.
Remove an archaicism (wheals)

Seems to have been a hardcoded reference to rotted corpses, which
no longer exist!
Fixup dragon hide/armour descriptions (9254)

Pearl dragon hide, shadow dragon hide, and steam dragon
armour/hide.
Allow batform players to memorize spells

Incredible buffs to the "vampire bat" conduct.
Turn unpetrifying tree-form players back to wood.
Turn player flesh into data

Re: de-petrification messages.

Only functional change is that shadow form now turns back to
shadow - though perhaps it shouldn't be petrifiable at all...?
Simplify (PleasingFungus).
Some minor mindexicide.
Use monster::move_to_pos more widely.
Add monster::swap_with, use it in several locations.
Improve Wild Magic card (theTower).

It now causes miscasts on enemies and restores magic for each one affected.
As it is no longer (entirely) bad, it is moved from punishment to wonders.
Also fixes monster malign gateway miscasts from being hostile towards the
player.
Implement and use fair_adjacent_iterator.

Also correcting the spore explosion directional bias introduced in
0.16-a0-2679-gdd6be42.
Simplify some set logic.
Don't pretend a few functions can fail.
Don't reduce crawlie merge chance when full aboms are adjacent.
Move statue and wisp form rPetrify into form data.
Make player shadows insubstantial (AreBrandon)

At least for rPetrify purposes.
Base panlord tile recolouring (roctavian).

To give them a colour that can be recoloured in dc-* tile directives.
Inherit panlord colours in tiles from console colour.

The exact colour adjustments should be cleaned up, but the basic
implementation is here.