SPIGOT-3699: Fix cloning banner itemstacks

the banner meta would end up with a shared reference to the patterns

Spigot-Server-Patches/Fix-cloning-banner-itemstacks.patch

@@ -0,0 +1,27 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Aikar <aikar@aikar.co>
+Date: Fri, 15 Dec 2017 15:52:28 -0500
+Subject: [PATCH] Fix cloning banner itemstacks
+
+the banner meta would end up with a shared reference to the patterns
+
+diff --git a/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaBanner.java b/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaBanner.java
+index aa1a210a2..3ae4604f0 100644
+--- a/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaBanner.java
++++ b/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaBanner.java
+@@ -0,0 +0,0 @@ public class CraftMetaBanner extends CraftMetaItem implements BannerMeta {
+     boolean applicableTo(Material type) {
+         return type == Material.BANNER;
+     }
++
++    // Paper start
++    @Override
++    public CraftMetaBanner clone() {
++        CraftMetaBanner clone = (CraftMetaBanner) super.clone();
++        clone.base = this.base;
++        clone.patterns = new ArrayList<>(this.patterns);
++        return clone;
++    }
++    // Paper end
+ }
+--