SPIGOT-5311: Add API to get/set item associated with throwable projectiles

By: Lars Dormans <lars.dormans@live.nl>

paper-server/nms-patches/EntityFireballFireball.patch

@@ -1,6 +1,6 @@
 --- a/net/minecraft/server/EntityFireballFireball.java
 +++ b/net/minecraft/server/EntityFireballFireball.java
-@@ -18,7 +18,7 @@
+@@ -18,14 +18,14 @@
  
      public void b(ItemStack itemstack) {
          if (itemstack.getItem() != Items.FIRE_CHARGE || itemstack.hasTag()) {
@@ -9,6 +9,14 @@
                  itemstack1.setCount(1);
              }));
          }
+ 
+     }
+ 
+-    protected ItemStack l() {
++    public ItemStack l() { // PAIL protected -> public
+         return (ItemStack) this.getDataWatcher().get(EntityFireballFireball.f);
+     }
+ 
 @@ -50,6 +50,6 @@
          super.a(nbttagcompound);
          ItemStack itemstack = ItemStack.a(nbttagcompound.getCompound("Item"));