New Engine Feature: EEex_AttackOnce

[4Luke4]

This PR introduces a brand new script action:

EEex_AttackOnce(O:Target*,I:BaseAttackRollMod*,I:OverrideBaseDamageRoll*,I:ConsumeAmmo*Boolean)

Vanilla Attack() that stops after the first real attack roll.

• I:BaseAttackRollMod*: can be used to modify vanilla base 1d20 attack roll
• I:OverrideBaseDamageRoll*: can be used to override base damage roll
  • If 0, then final damage will be 0 too (regardless of all the other modifiers)
  • If negative, then no change (keep vanilla roll)
• I:ConsumeAmmo*Boolean: can be used to force ammo consumption (in case of ranged / thrown weapons)
  • Will be ignored in case of special ranged weapons such as Quiver of Plenty +1

Needed for: Bubb13/EEex#136.