rough implementation of newskald spells

new spells: infusion, song of slaying, spectral weapon, spirit shield
new book: book of battle
new mons: MONS_SPECTRAL_WEAPON
slightly improved behavior for spectral weapon

the weapon will now approach attacked monsters in more situations, but still a weird problem exists where it gets "stuck" behind you occasionally...
Give layout_gridlike wider paths in deeper levels

Corridors can be up to ceil(depth/3) width.
Revert accidental commits of unfinished code.

This reverts commit 2313bf4df8ea083a227b5138f135314216ba1929.
This reverts commit 2c9fbfe1adc839f19fd42e7fe7c93c986be4e873.
Axe some more unfinished code that the previous revert failed to revert.

This reverts commit 2313bf4df8ea083a227b5138f135314216ba1929.
Berserkitis Reform

Do not berserk when fighting firewood.
Give Blade triple swords, prevent type/ego duplication.
Vary layout_gridlike room shapes and add some per-branch variations

Also enabled it in Crypt and made it substantially more likely in Elf
Add a config option to allow undoing item glyph recolouring.

It's misnamed "0.12_monster_glyphs" for consistency with other such files,
even if it has not a single monster inside.

Having to list every fixed artefact is not nice, so some suggestion would
be good: it's not as straightforward as adding a "non-artefact" tag as no
one uses anchors so it'd match "artefact", and other tags wouldn't be
obvious enough.
Restore goddamned_bats.

Not because it's the best vault, but because it's a prominent reference
to a part of Crawl's history.  It has none of stated problems: corpses
work well, there are no "comes into view" problems (because of the genus
being correct).

This vault's removal has attracted a surprising amount of criticism, mostly
for emotional reasons, and not a single voice of approval.

I do agree some parts are silly, though: fruity bats and dwarf mountain bats
are ones I personally wouldn't shed a tear after.
Restore kb_skeletal_archery.

I think it's a good example of well designed one-off monsters:
* players intuitively know what the monster is, what to expect from it,
  and what it looks like, without having to read the description, or
  worse, spoilers.
* if they remained as plain "skeleton warriors", folks who play fast
  would be penalized for not reading that "comes into view, wielding
  a longbow" or being spoiled
* the vault actually provides some challenge: meeting a firing line
  can be deadly if you act stupidly

The vault could be made more aesthethic, though.
Remove an unused macro.
Fix spell-related commands being incredibly spammy if you know IMB.
Use 30 for sanity caps of all item enchantment types.

It was 30 for weapons, 25 for armour, which caused spam with Lear's.
Don't test missile enchantment values.
Reduce staff of energy hunger to zero once again.
Merge staves of energy and channeling.
Don't let mutations and vigour affect staff/rings of power.
Make staff of power's effect increase with your maxmp.

It gives 5 + 0.4 * maxmp, with anything above 50 being halved.
Formatting fixes.