WIP: PlayerCanBust hook

A hook that executes when a player makes contact with an existing FF_BUSTUP FOF. The function provides both the player and the FOF in question; returning true forces the block to be busted, and false forces it to not be busted.

The reason why it's a WIP as of now, though, is a matter of which blocks would it be useful to apply to: currently FF_SHATTER and FF_SHATTERBOTTOM blocks are excluded from its scope. I'm accepting feedback on that and what other features it could include.