Update upstream CB/S

--- work/CraftBukkit
Submodule work/CraftBukkit 297ff400..83af86db:
  > SPIGOT-5457: Downgrade 'Mismatch in destroy block pos' message to debug
  > SPIGOT-5481: PlayerBedLeaveEvent returns wrong bed location
  > SPIGOT-5482: Structure Block setUsageMode encounters NullpointerException
  > SPIGOT-5426: isSimilar for player heads fails
  > SPIGOT-5478: XP not dropping when a player dies

--- work/Spigot
Submodule work/Spigot 05bb8bcf..492a7792:
  > Rebuild patches

Spigot-Server-Patches/PlayerDeathEvent-getItemsToKeep.patch

@@ -8,7 +8,7 @@ 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/net/minecraft/server/EntityPlayer.java b/src/main/java/net/minecraft/server/EntityPlayer.java
-index ed1c37bee9..ba30730b5a 100644
+index ebab423af..f482bb6cb 100644
 --- a/src/main/java/net/minecraft/server/EntityPlayer.java
 +++ b/src/main/java/net/minecraft/server/EntityPlayer.java
 @@ -0,0 +0,0 @@ public class EntityPlayer extends EntityHuman implements ICrafting {
@@ -59,7 +59,7 @@ index ed1c37bee9..ba30730b5a 100644
      public void die(DamageSource damagesource) {
          boolean flag = this.world.getGameRules().getBoolean(GameRules.SHOW_DEATH_MESSAGES);
 @@ -0,0 +0,0 @@ public class EntityPlayer extends EntityHuman implements ICrafting {
-         this.releaseShoulderEntities();
+         this.dropExperience();
          // we clean the player's inventory after the EntityDeathEvent is called so plugins can get the exact state of the inventory.
          if (!event.getKeepInventory()) {
 -            this.inventory.clear();