Revert "Bye bye clinging."

Clinging might be a minor feature, but it's a distinguishing one, it's thematic
and it's working quite well.
Player/monster symmetry has never been a goal, so it seems dubious to invoke it
as the reason to throw away all the work that has been put into clinging. We
can always say that the player turns into a different kind of spider which is
unable to cling for some reason.

This reverts commit bdc56382eacf7af1b2330dc6444916d368741fec.
This reverts commit d689486464fcaaac025a6f469ab69674a2f4d173.
This reverts commit 1addaaf8ee92de5060fdb436f93251843abd2035.
Add a missing NSUBST to grunt_vaults_end_simple_division (#7403).

Oops.
Axe an unused function.
Revert "Remove player clinging".

Minus gargoyle clinging, of course.

With monster clinging back, it would be inconsistency for inconsistency sake.

Player clinging:
* is what people expect spiders to be able to do (if monsters can).  Count on
  bug reports about this.
* allows people to learn monster mechanics on their own
* is useful in the early game, or later if you don't have that particular
  spell.  People don't tend to lug heavy potions of Flight either.
* is actually fun
Don't let unborn drop invalid corpses.
Reduce the weight of encompass vaults on D:$.

By all indications, they're turning up way too often there with the
changes that treat Zot entries as D branch endings.

Either that or people remember profane_halls and pleasuredromes a lot
better than the other Zot entries.
Allow tentacle kills to damage their parent (#7455)

We were failing to pass the damage up if the tentacle died.  That could
have encouraged trying to damage the tentacle for slightly less than its
current hit points.

The damage was already capped at the tentacle's remaining HP.
Unmeld boots when fishtail merfolk transform (#7456)
Remove an in-game use of gamer slang (VolteccerJack)
Make a randbook phrase more idiomatic.
Remove boring beetles from Vaults spawn list (ontoclasm)

There's not much boring for them to do there.
Don't give Confusing Touch when Zin prevents fungus form (#7461)
Make rings and armour of see invis work for monsters.

Monsters without innate SInv already valued the rings, and the
corresponding artefact property already worked (though it did
not respect suppression; this is also fixed).
Identify scrolls of amnesia if read with no spells memorised

It was unlikely to be ambiguous very often anyway since almost all scrolls that
don't target an item are always identified on-use anyway.
Allow selecting a weapon when reading ?vorpalise

This allows cancelling the scroll by swapping to a non-weapon, or choosing
a desired weapon to vorpalise.
Don't allow cancelling the refrigeration effect from ?vorpalise

None of the other explosions are cancellable in this way, and they can
all now be avoided if allies are nearby by cancelling the scroll when
asked to select a weapon, anyway.
Fix ?vorpalisation and the Blade card taking less time when swapping weapons
Reduce item destruction chance for AC characters

Elemental beams hitting the player now only destroy items when players
fail (damage after AC and resists) chance_in random2avg(raw damage, 2).
This does not apply to acid attacks or sticky flame, even if the latter
could definitely use some clever stuff to make it less annoying.

High-EV characters can often avoid the destruction blows entirely.
This change tries to address a perceived imbalance which means that you
hopefully now will see messages like
    The puff of flame hits you!
   _Five of your 7 scrolls of immolation catch fire!
less often when taking no substantial damage from the beam.
Don't let resists reduce item destruction chance.

Adjust the previous commit to look at the post-AC damage rather than the
final damage.  Also, use pre-AC damage as the denominator, so that
damage_funcs don't reduce the apparent effect of AC.
Improve Wyrmbane's description.

Wyrmbane can only gain enchantment when it kills a dragon who's HD are
higher than Wyrmbane's current enchantment level. The description should
hint at this.