Fixed bad overrides of getBoundingBox()

src/pocketmine/block/BrownMushroom.php

@@ -67,7 +67,7 @@ class BrownMushroom extends Flowable{
 		return false;
 	}
 
-	public function getBoundingBox(){
+	protected function recalculateBoundingBox(){
 		return null;
 	}
 

src/pocketmine/block/Liquid.php

@@ -442,7 +442,7 @@ abstract class Liquid extends Transparent{
 		}
 	}
 
-	public function getBoundingBox(){
+	protected function recalculateBoundingBox(){
 		return null;
 	}
 

src/pocketmine/block/SignPost.php

@@ -55,7 +55,7 @@ class SignPost extends Transparent{
 		return "Sign Post";
 	}
 
-	public function getBoundingBox(){
+	protected function recalculateBoundingBox(){
 		return null;
 	}