We always created a new vector object instead of changing the passed in vector directly. This works for the function being called using our changed values - but the caller doesn't see the changed values if it's passing a vector by reference.
Only create a new vector if there isn't one being passed in and set the values directly in the passed in vector otherwise.
* DHooks: Allow setting CBaseEntity* param to NULL #1751
The param had to be a valid entity and wasn't allowed to be set to NULL. Behave similar to SetReturn which maps INVALID_ENT_REFERENCE (or -1) to NULL.
* Update include documentation
