Fix DamageWeapon

[kphoenix137]

DamageWeapon() is very repetitive and has some bugs:

• Dual wielding can result in the right hand item not losing damage %/durability on attacks
• Indestructible items with a current durability < 255 can lose durability and be destroyed
• Inconsistent durability conditions (<= 0 VS == 0)

DecayWeapon() isn't really needed and just adds additional complexity. It can safely be nested in DamageWeapon()'s for loop in the refactored function, preventing the need for an additional for loop for the purpose of checking all hand items while dual wielding.