Spells/Feeblemind: Fix calculation of the effect and it's duration.
Duration: [[Evaluating Intelligence / 5] + 1] * 6)
Effect: 8 + [Evaluating Intelligence](Caster's) / 10 - [Resisting Spells](Target's) / 10)

Signed-off-by: Kitiara <vinas_solamnus1@hotmail.com>