Fix ability letter save-compat for jump removal.
Clarify the consequences of decapitation

In Hydra Form.

Bonus: Also reveals a previously semi-secret monster hydra
mechanic! (Healing when their heads are lopped off.)
Add a temp param to holiness
New spell: Irradiate

Level 5 Conj/Tmut. Does heavy damage to adjacent foes (and
malmutates them, for flavour), but contaminates the caster; 2-4
casts will put you into yellow contamination. Design goal: play
around with contam mechanics and tmut/contam interactions & add
a neat tm support spell.

Currently in the Book of Alchemy and the Book of
Transfigurations. (Ice Form has been moved from the latter to the
Book of Ice, per Grunt's suggestion.)
Rework monster malmutation

Now that it's an actual effect that will actually appear in games
(irradiate), it should probably be made sane.

Changes:
- Action speed penalty (-1/stack) removed.
- AC penalty increased to -4/stack. (From -1/stack.)
- Damage penalty removed, for gross crimes against good coding.
  (Was -10%/stack, to max of -50%).
- HD penalty added; -10% stack, to max of -50%. Applies after
  draining, to avoid undue synergy.
- Effect made temporary; celebrate, Beoghites!
Tidy up an unused parameter
Use calcdice (|amethyst)
Remove flavour restrictions on Irradiate

Too much antisynergy with other tmut spells, & the undead stuff
may be a premature reaction to potential abuse. Will keep a close
eye on the latter.
Tweak Irradiate description