[GAMEPLAY] Gangplank is critting structures.

https://www.youtube.com/watch?v=JyQIwjisJUU

Vandiril does some great work. GP is currently critting turrets, inhibitors, and the nexus via auto-attack cancelling on his barrels.

[How To Reproduce]

1. As Gangplank, place a barrel beside the structure.
2. Begin to auto-attack the barrel.
3. Cancel the auto-attack by switching targets to the structure.

If the auto-attack on the barrel would have crit, the attack on the structure will crit. Since GP builds crit via Statilkk Shiv, Phantom Dancer, and Infinity Edge, it is incredibly easy to abuse this bug.