Update Bukkit to 1.6.4
Display correct effect duration in seconds. Fixes BUKKIT-3983
Actually display correct effect duration in seconds. Fixes BUKKIT-3983
Use simple multiplication for squaring. Fixes BUKKIT-4836

This change adds a method to NumberConversions for squaring and
replaces uses of Math.pow(..., 2) with the new method for efficiency
reasons.
Merge remote-tracking branch 'upstream/master'
Tukkit Updates