Properly implement type-boosting items in Generation 3

[vivapuffs]

No description provided.

[vivapuffs]

jetou informed me that the problem is actually on the sim's end and not the calc's end, so i'm closing this pr

[thejetou]

For more information, here's the reason for the discrepancy.

PS is chaining the modifiers (search 'chaining' in DaWoblefet's damage dissertation for an explanation) but this only happens in Generation 5 and up while in Generation 4 and below it's just sequential arithmetic operations.

Reading the Emerald source code it's implemented the same way as in the damage-calc by multiplying with 1.1 essentially.

Thank you for the PR, but this will have to be fixed on the PS side.