LUSpellSelection: comment out unused global

possibly a todo, since all existing sorcerer-style spellbooks have
different progression than the mx tables
iwd2::cg: don't allow sorcerers to learn too many new spells
OpenSpellsWindow: get the spellbook type via argument instead of deduction

sorcerers spoiled this
Spellbook::AddKnownSpell: fix iwd2 druid spellbooks

their constant overlaps with bg2 innates
iwd2::cg: fixed the bio lookup in RevertPress