Reuse buffers for chunk compression to optimize memory use

Instead of allocating a buffer for every chunk compression, reuse
the same 64k sized buffer.

Also stopped doing dynamic compression levels. It wasn't helping enough.

This will improve memory usage and zlib performance of chunk compression.

Spigot-API-Patches/0181-PlayerDeathEvent-getItemsToKeep.patch

@@ -1,4 +1,4 @@
-From 9552cb45732ed2d11f179cdf766996d3c0843001 Mon Sep 17 00:00:00 2001
+From f3ebc45b923294990f9db2b1514d34d7c9a4840f Mon Sep 17 00:00:00 2001
 From: Aikar <aikar@aikar.co>
 Date: Mon, 11 Mar 2013 20:04:34 -0400
 Subject: [PATCH] PlayerDeathEvent#getItemsToKeep
@@ -8,10 +8,10 @@ Exposes a mutable array on items a player should keep on death
 Example Usage: https://gist.github.com/aikar/5bb202de6057a051a950ce1f29feb0b4
 
 diff --git a/src/main/java/org/bukkit/event/entity/PlayerDeathEvent.java b/src/main/java/org/bukkit/event/entity/PlayerDeathEvent.java
-index 5b0ef1eb1..b30818177 100644
+index 5b0ef1eb..af6070d1 100644
 --- a/src/main/java/org/bukkit/event/entity/PlayerDeathEvent.java
 +++ b/src/main/java/org/bukkit/event/entity/PlayerDeathEvent.java
-@@ -18,6 +18,22 @@ public class PlayerDeathEvent extends EntityDeathEvent {
+@@ -18,6 +18,40 @@ public class PlayerDeathEvent extends EntityDeathEvent {
      private boolean keepLevel = false;
      private boolean keepInventory = false;
  
@@ -19,9 +19,27 @@ index 5b0ef1eb1..b30818177 100644
 +    private List<ItemStack> itemsToKeep = new java.util.ArrayList<>();
 +
 +    /**
-+     * A mutable collection to add items that the player should keep on death (Similar to KeepInventory game rule)
++     * A mutable collection to add items that the player should retain in their inventory on death (Similar to KeepInventory game rule)
 +     *
 +     * You <b>MUST</b> remove the item from the .getDrops() collection too or it will duplicate!
++     * <pre>
++     *    \@EventHandler(ignoreCancelled = true)
++     *     public void onPlayerDeath(PlayerDeathEvent event) {
++     *         for (Iterator<ItemStack> iterator = event.getDrops().iterator(); iterator.hasNext(); ) {
++     *             ItemStack drop = iterator.next();
++     *             List<String> lore = drop.getLore();
++     *             if (lore != null && !lore.isEmpty()) {
++     *                 if (lore.get(0).contains("(SOULBOUND)")) {
++     *                     iterator.remove();
++     *                     event.getItemsToKeep().add(drop);
++     *                 }
++     *             }
++     *         }
++     *     }
++     * </pre>
++     *
++     * Adding an item to this list that the player did not previously have will give them the item on death.
++     * An example case could be a "Note" that "You died at X/Y/Z coordinates"
 +     *
 +     * @return The list to hold items to keep
 +     */