XGUnitNativeBase::TriggerOverrideProjectileInstance is bugged

[Iridar]

Relevant code.

Original issue: #829

The docs mention that the purpose of this override is to allow listeners to override parameters of the original function, but the override obviously doesn't function like that, as none of the override arguments are set as out, and are not updated after triggering the event.

Moreover, the bPreventProjectileSpawning parameter is not updated after triggering the event either, so the advertised functionality of being able to prevent the projectile from spawning doesn't work.

This can be addressed in two ways:

1. Conservative - update bPreventProjectileSpawning and correct docs by removing the "override parameters" line.
2. Expansive - convert all override arguments to out and update all of them after triggering the event.

Suggestions, preference?