Update CraftBukkit to Minecraft 1.5.2
Fix things using wall time running too fast. Fixes BUKKIT-4155

When converting things in Minecraft to use wall time instead of ticks I
realized we'd run into integer division rounding issues and could have
updates that end up counting as zero ticks. To compensate for this the
code ensures we always process at least one tick. However, every time we
end up with zero ticks the next time we have an extra tick due to rounding
the other way with the leftovers. This means we are going far too fast and
should not have this at least one tick logic at all.

On top of this some potions rely on the number of ticks they run and not
just the amount of time they last and so potions were put back to running
with ticks entirely.
Revert "Add delay to hopper even if it doesn't do anything."

This reverts commit f5388e8f94e2cbab76c2255fd872c289e83100a0.
Always process movement for vehicles and passengers. Fixes BUKKIT-4142

As an optimization we don't do any movement processing on entities that
have not moved. However, players in minecarts trigger this condition when
the minecart is moving on its own. This causes issues with things that rely
on player collision like tripwires. To correct this and any future related
issues we always handle movement for passengers and their vehicles even
if one of the two hasn't moved since they are linked.
Move world generator warning to CraftBukkit. Fixes BUKKIT-2565
Improve InventoryCloseEvent handling. Fixes BUKKIT-3286

Currently there are several cases where a player will have their inventory
screen closed client side but we will not call an event. To correct this
we call the event when the server is the cause of the inventory closing
instead of just when the client is the cause. We also ensure the server is
closing the inventory reliably so we get the events. Additionally this
commit also calls the event when a player disconnects which will handle
kicks, quits, and server shutdown.
Fix animal spawning ignoring limits. Fixes BUKKIT-4180

Minecraft 1.5.2 changed mob spawning by ignoring persistent mobs from the
mob count. In CraftBukkit all mobs that previously used a separate hard
coded persistence system were ported to instead use this one. This causes
all animals to be persistent by default and thus never be counted. To
correct this issue we consider if the mob would be considered persistent
in the hard coded system as well when deciding if a mob should count.
Fix typo/logic error in previous commit
POM Changes
mc-dev imports
Spigot Changes
Proxy IP Filter
Merge tweaks and configuration

This allows the merging of Experience orbs, as well as the configuration of the merge radius of items. Additionally it refactors the merge algorithm to be a better experience for players.
LongHash Tweaks.

This commit adds a flat array based cache to the LongHash(Set/Map) classes leading to excellent efficiency for servers where most activity is centered around the origin (0,0)
Async Operation Catching

Catch and throw an exception when a potentially unsafe operation occurs on a thread other than the main server thread.
View Distance

This commit allows the user to select per world view distances, and view distances below 3. Be wary of the issues selecting a view distance of 1 or 2 may cause!
Implement 'lightening' of NibbleArrays - only allocate buffers when non-trivial value Saving from 40-45% of memory use by chunk section data.

Finish up NibbleArray lightening work - use for Snapshots, reduce copies

Fix nibble handling with NBT - arrays aren't copied by NBTByteArray
Optimize packet used to unload chunks for the client

At the moment telling a client to unload a chunk involves calling the entire chunk from memory, deflating it and then sending it through the pipes even though the client ignores it and based on the bitmap simply unloads the chunk, and to add the cherry on top, this is done on the main server thread.
Alternate, sync-free-but-safe chunk reference cache
Tick loop optimization - sleep for as long as possible.