Prune duplicate code for LOS attack spells.

This commit merges the handling for Drain Life, Ozocubu's Refrigeration,
and Olgreb's Toxic Radiance, which shared a lot of duplicate code, into
one code path. This includes the player and monster implementations of
these spells.

Yes, this means monsters can now cast OTR (watch out for rods of
venom!); the tweaks to allow ghosts to do this are in place as well.

This changes the signature of the dlua function spells.toxic_radiance;
as far as I am aware this function is not currently used anywhere. (Now,
who wants to start work on Olgreb's Toxic Radiator?)
Switch Vehumet-gifted spells to use the memorization interface (elliott).

Also, now there is no time limit on memorizing the offered spells, though
they will be overwritten by new offers.
Allow memorizing a Vehumet gift even at 100% fail.

The alternative is not to gift spells at 100% fail, but that might cause
players to wear/not wear wizardry to try to control their gifts. Besides,
Vehumet wizardry makes it feasible to get any spell usable with a little
time.
Remove a magic number for Vehumet piety.
Fix tiles compilation.
Memorise ability tile
Hilight Vehumet gifts in the tiles mem. tab
New unique: Jorgrun, the dwarven earth elementalist.

Spells: Iron Shot, Petrify, Stoneskin, LRD, Shatter, Blink (as escape).
New unique: Lamia, as a naga queen.

Lamia can be thought of as a "greatest naga", though differentiated
through the spell set - which is comprised of IOOD, Mesmerise, Haste,
Olgreb's Toxic Radiance, and Teleport Self as an emergency spell. She is
generated with a naga barding, one of a halberd, glaive, or bardiche,
and a band of followers up to and including greater nagas.

She also can eat corpses, so she can, in fact, eat her own children.
Chaos butterflies!

They are similar to some of the moth enemies, possessing a chaos attack
and the special ability to be constantly surrounded by rain clouds (similar
to Asmodeus and his ring of flames), as well as the ability to summon
twisters.

They are considered abyssal monsters.
Tiles for Jorgrun and Lamia; use colour-cycling butterfly for chaos butterfly.

The two new tiles are variants of the deep dwarf necromancer and greater
naga respectively. Feel free to come up with something better in their
place.
Don't ignore chaos butterflies by default for autoexplore purposes.

This changes the runrest_ignore_monster default setting to strictly
match butterflies alone instead of any monster with butterfly in the
name.
Tag Jorgrun with M_NO_REGEN.

He's a deep dwarf, so he shouldn't regenerate.
Fix indentation.
Flip something_under, new_stair
Weight Vehumet spell gifts based on your elemental skills.
Display disjunction properly in WebTiles
Tag chaos butterflies with M_NO_POLY_TO.

As pointed out by elliptic, having shapeshifters pollute, say, branch
ends with water and twisters just isn't a good idea.
Increase the elemental weighting for Vehumet gifts.
Increase the size of the Vehumet gift timeout.

People were getting all their gifts before finishing Lair.