1.15.2 update (#2887)

Functional GUI fix added by billygalbreath

Spigot-API-Patches/Fix-upstream-javadoc-warnings-and-errors.patch

@@ -6,7 +6,7 @@ Subject: [PATCH] Fix upstream javadoc warnings and errors
 Upstream still refuses to use Java 8 with the API so they are likely unaware these are even issues.
 
 diff --git a/src/main/java/org/bukkit/World.java b/src/main/java/org/bukkit/World.java
-index df4caf29..ca60c514 100644
+index edd73f41..220420ed 100644
 --- a/src/main/java/org/bukkit/World.java
 +++ b/src/main/java/org/bukkit/World.java
 @@ -0,0 +0,0 @@ public interface World extends PluginMessageRecipient, Metadatable {