Switch Ru's muting effects to antimagic

Mute was being applied to creatures that can't be muted (demons, dragons)
and also mute just didn't limit enough cases. This switches the effect
to antimagic, adjusts the messages, applies proper checks for valid
targets, and greatly increases the duration because antimagic isn't
absolute.
Improve Ru retaliation messages.
Improve loot for one stingy Lair end vault (crate)
Don't crash when swapping an ally onto a shadow/spider trap.

They would trigger the trap before the player is moved into place,
potentially summoning something on top of the player's location.  See
for example:
  http://crawl.akrasiac.org/rawdata/FACE/crash-FACE-20141228-180029.txt

There is still a crash here, which is more difficult to solve.  If you
were standing on a toadstool (atop the trap) and swap with a wandering
mushroom, the mushroom will again trigger the trap before moving the
player.

Related, if you are atop a toadstool and the mushroom is on a trap,
then swapping with the mushroom triggers the trap twice: once for
the toadstool and once for you.
Don't crash when swapping mushrooms onto toadstools on traps.

Also, don't double-trigger traps when you and a toadstool swap with a
mushroom onto the trap.

These are the two cases mentioned in the previous commit.
Add some XXX-rated comments
Brace
Fix book naming

This is very silly...
Erp
Don't turn all items into books
Fix a sign warning.
Tweak tutorials 1 and 2
Remove a fixed FIXME
Fix most -Wparentheses warnings.

This fixes all of the -Wparentheses warnings except "suggest parentheses
around && within ||"; in my opinion, fixing those would make our logical
expressions harder to read, not easier, because of all the extra
parentheses.
Don't place clouds when relocating monsters after Chei abils.

Also avoid teleport messages if the blink failed.

The blink part is a hack:
<PleasingFungus> probably the Right Solution is to have some kind of
  "move monster to nearby square" function that both chei & blink_to()
  call
Remove a blinding book tile

Literally painful to look at.
Fix a probable precedence error.

bh couldn't remember for sure, but it is very likely that the 3 here was
supposed to be a minimum.  But & has low precedence, close to that of &&
Delete crawlcode
Let monsters cast prisms non-adjacent to their foe.
Don't try to fire a tracer for Fulminant Prism.

It doesn't work unless the caster and target and chosen position are lined
up just right, since the tracer doesn't explode.

There does need to be some kind of check to avoid hurting allies (and
oneself), but probably _mons_prism_pos would be the place to do that.