Remove Nagas from Guardian Serpent bands

There's apparently a push to reduce the number of chaff
nagas from Snake. This removes ordinary nagas from Guardian
bands and replaces them with professional nagas.

This idea comes from HangedMan, so throw vegetables at him
if it isn't to your liking.
Raiju Tweaks: Damage and HD

Adjust Raiju HD upward while nudging its damage downward.
I'd like them to be roughly on par with Smoke Demons. At
the moment, their kills seem to exclusively be low level
abyss knights wandering around when they shouldn't, or
simply incidental to players getting mobbed. This isn't
to say that player kills is a good metric for judging
monsters, but I want to ensure that they're a threat
worth taking seriously.
Rebalance mid-tier abyss monster weight

Split the weight between some mid-tier abyss monsters:
raiju, smoke demons and that unspellable mutator demon.
Smarter Blinkbolt

Don't blink blinkbolt users into lava or other leathal
squares. If blink can't find a place to put the caster,
traverse the lightning path backward until you find a
safe square.
Simplify.
Don't go out-of-bounds in wrapcprintf (#7637)

And constify, lift things out of loops, etc.
Enable several splash screens accidentally omitted from builds.

You already saw them if you played from your build directory, so many of
us thought they were already enabled.
Enable pooryurik_knight title screen too.

Unlike the others, it was intentionally not enabled (see
0.12-a0-273-g5c8ac43), but since do-it-yourself trunk players have been
seeing it for a while anyway, I think there's no point to keeping it
disabled.
Avoid a beholder/fearmonger crash (#6547)

When removing the last beholder or fearmonger, we could print a message
before setting DUR_MESMERISED|AFRAID to zero.  If that triggered a
redraw of the status area, the inconsistent state would trigger an
assertion.

Now quietly remove the status before messaging about losing the
beholder.
Minor tweak to armour_ego_name/weapon_brand_name

Don't include brackets for the terse version. Easier to add on calling
side when required than to remove when not required.
Annotate items with terse description of their ego

Purpose of this is allow finding for example helmet of see invisible by
searching for "SInv".
Don't prepend " of " in weapon_brand_name
Plug one case that relied on the exact order of radius_iterator.

This plugging is quick and dirty, we can optimize it later.  This part
of the code is performance sensitive.  Even this plugging is much faster
than the old radius_iterator though: it did the full square, did double
squaring for every position in it, etc.
Rewrite the radius_iterator.

No rectangle_iterator, no circle_iterator nor circle_def, no los_glob with
an internal radius_iterator then los_base; not even a single multiplication
inside a loop (although the last part is negligibly small compared to a
typical user).

And lookie at this such simple code.  It is simple, without nothing naughty
behind these macros, right?  Right???
Drop the now unused circle_iterator.

It turns out it was only an implementation detail of radius_iterator.
Drop los_glob.
Make los_def not use virtual methods.

They don't belong in performance sensitive code... and the only other class
derived from los_base just became 404-compliant.
Don't list potions of slowing in \- (78291)
Fix a weapon name error I just introduced

So no more "flail of ".
The Slimy Ring of Jiyva

An unrand ring: {rMut contam MR}
rMut ceases to function if you murder Jiyva.