Force compile-time failures for the subtle changes done in the API

By: Erik Broes <erikbroes@grum.nl>

paper-api/src/main/java/org/bukkit/event/block/BlockListener.java

@@ -1,6 +1,7 @@
 package org.bukkit.event.block;
 
 import org.bukkit.event.Listener;
+import org.bukkit.plugin.AuthorNagException;
 
 /**
  * Handles all events thrown in relation to Blocks
@@ -32,10 +33,16 @@ public class BlockListener implements Listener {
      * Called when a block flows (water/lava)
      *
      * @param event Relevant event details
+     * @throws BukkitAuthorNagException 
      */
     public void onBlockFromTo(BlockFromToEvent event) {
+        onBlockFlow(event);
+        throw new AuthorNagException("onBlockFlow has been deprecated, use onBlockFromTo");
     }
 
+    // Prevent compilation of old signatures TODO: Remove after 1.4
+    @Deprecated public final void onBlockFlow(BlockFromToEvent event) {}
+
     /**
      * Called when a block gets ignited
      *