WORLDGUARD-3100 - Reported by PseudoKnight

Suggested in the forums by jambasparabolp
http://forum.sk89q.com/threads/worldguard-flag-idea.15538/

Unfortunately there's no event for this and so perhaps repair damaged anvils on player interact events. So while it wouldn't exactly do what it sounds like it does, 'anvil-break' is probably the more intuitive name for it so that they can set it to 'deny'.