Unhide a hidden item in due_jungle_book

The item surrounded by trees is now at least visible without reading the
vault desc.
Improve flavour of reanimated macropods.
Suppress distortion unwield effects for Lucy followers.

In my observations of relatively recent wins by Lucy followers, very few
actually bother to take advantage of the 6* gift; this might partially
be on account of the limitations of the brand itself, but even for
weapons which pair well with it (fast-hitting weapons, axes, and the
like) players prefer other brands. I theorise this is partially on
account of being effectively restricted to use of the one weapon if the
player doesn't want to be subject to extreme negatives.

I've run this idea by quite a few people and there doesn't seem to be
any negative feedback on it as yet, so I think it's worth giving a try.
Use -isystem instead of -I for (what should be) system libraries

This includes contribs.

We don't do this for system sqlite, though, since that's expected to
be either in /usr/include et al or from contribs, and explicitly
passing "-isystem /usr/include" screws up the include path ordering.

(Instead, we drop the -I flag for sqlite entirely.  If it turns out to
be needed somewhere, the comments were wrong ...)
libunix: drop now-unneeded "#pragma GCC diagnostic" junk
Add Ribbit sewer vault.

[Committer's node: made the following changes:
 * Removed some stray permarock (where giant frogs would be).
 * Removed the PLACE: D:6
 * Fixed some stray whitespace
-nfm]
Add a Kobold Necromancer sewer vault

[Committer's note: made the following changes:
 * Named the monster "big kobold necromancer".
 * Set the weight fairly low.
-nfm]
Allow delayed_decay to work with , and / itemspecs.

Several existing calls used something like:
  dgn.delayed_decay(_G, '%', 'human corpse / human skeleton')
But that actually only added never_decay to the corpse, not the
skeleton.  Now add delayed_

Also add a new function dgn.delayed_decay_extra, like delayed_decay
but taking one additional argument: a string listing additional
non-corpse items to place on the spot.  If the argument is not nil,
it is appended to the itemdef with a comma.  Use this for cases
like 'human corpse, battleaxe'.

Finally, for the few cases that used something like "human corpse / nothing",
use a SUBST to get the same weights.
Use delayed_decay in sewer_kobold_necro_badplayer.
Document delayed_decay changes.
Let ghosts of axed monsters walk through walls.

They may have been rock worms in a previous life.  Hopefully with the
removal of wall shielding this won't be too annoying.
Fix special_room_morgue for delayed_decay changes.

Use a few substitutions instead of having / nothing in the decayed_delay
spec.  For simplicity, we no longer place corpses on the stairs.

Also fix a stray whitespace in the delayed_decay implementation.
Message for restore abil partially curing draining
Hopefully fix reST syntax
Use rc settings for tile scaling in WebTiles

tile_cell_pixels and tile_filter_scaling
Move WebTiles glyph mode setting to rc file

Also axe a tile_force_regenerate_levels sighting.
Add a JavaScript function for testing changing options
Move WebTiles animations setting to rc file
Remove remaining traces of WebTiles settings window
Add tile_realtime_anim and tile_display_mode to init.txt