Added IsBuffSpell(spell_id). This will return true if the spell would end up having a duration, which will mean it would end up in one of the many buff windows on the client. This just makes sure the spell has a buffduration or buffdurationformula, which means the calculation will return a duration
Replaced all instances of CalcBuffDuration being used to determine if a spell was a buff with IsBuffSpell
Removed Mob::HasBuffIcon since it does the same thing IsBuffSpell does in a more convoluted way and had a rather missing leading name
Fixed issues that arose from the 10/03/2013 changes