FIX'd
Rename two functions.

They don't actually have anything to do with noise...
Staticalise.
Make servitor spell selection deterministic again (wheals).

If your failure rate for a servitor spell is below 50%, it's eligible
for inclusion.
Chimeras get all spells and abilities from their component monsters.
Scale chimera spell/ability frequency with number of spellcasting parts.

... so that the sum of spell/ability weights doesn't exceed the total
weight of 200.
Account for MON_SPELL_DEMONIC better in spellcasting messaging.

Useful for demon chimera spell messaging, not that that will ever come
up in normal gameplay.