atmos: fix a geometry error

reverse_dir is a list of reversed dir fields

Signed-off-by: Mloc-Argent <colmohici@gmail.com>
turf: adds a damage model for walls

New proc for walls: take_damage().
Damage is tracked in the "damage" var, walls will break if "damage"
 hits "damage_cap".
Damage can be repaired with a weldingtool.
Damage overlays are cached in the global wall var "damage_overlays"
 to reduce overhead.

Signed-off-by: Mloc-Argent <colmohici@gmail.com>
atmos: make fires more destructive

Fires can now burn through walls, windows, and (with a high enough
 temperature) rwalls.
New proc: adjacent_fire_act().  Called on turfs that a fire isn't able
 to spread to. (walls, floor surrounded by windows, etc.)

Signed-off-by: Mloc-Argent <colmohici@gmail.com>
Merge pull request #5343 from Mloc/bs12-burn

Fire buffs, wall damage