Injury Mirror is a god ability.
Fix an mprf.
Add MON_SPELL_BREATH.

Does more or less what you might expect; makes the spell slot subject
to a breath timer. Also removes a function that seems now-redundant.

The only gameplay change should be that hellephants and nagas now have
timers for their breath weapons.
Don't call fixup_spells() on everything on every reload.
Display some useful info about spell slots on wizmode xv.
Remove M{F,}_SPELLCASTER.

It more or less meant "is this monster able to cast spells?"; that
question is perfectly well-served by looping over the monster's spell
list and seeing if any of them are not SPELL_NO_SPELL. The slight
performance hit is, I think, compensated by not having the confusing-ness
of the name (attack.cc had one case where can_use_spells was treated as
is_actual_spellcaster, for instance.)

The only intended change in gameplay is a slight change in how
polymorphing unique works: the new monster no longer has only half a
chance to cast, it only keeps the spells of uniques (I'm not certain,
but I think it used to keep the spells of vault monsters?), and there
may be some corner cases where the unique loses its spells, where before
it simply would not cast them (this would matter, for example, if it
were later polymorphed into a form that could cast them).
Remove a redundant-looking block of code.

It seems this would stop monsters with a wizard spell from using even
innate abilities while silenced (there's a check for silence just below
the removed block).
Variable-length monster spell lists.

Allows for more or less than six spells to be defined. Hooray.
Let naga (battle)mages spit poison.
Tag monster uses of teleself with MON_SPELL_EMERGENCY.

Possibly could use a SPFLAG_ONLY_EMERGENCY or similar.
Unbreak monster spell display.

In multiple senses.