Add renamed OPEN_SIGN_ENTITY packet for backwards compat

Fixes #243

Author: dmulloy2

modules/API/src/main/java/com/comphenix/protocol/PacketType.java

@@ -222,6 +222,12 @@ public static class Server extends ObjectEnum<PacketType> {
 			@Deprecated
 			public static final PacketType STATISTICS =                   STATISTIC.deprecated();
 
+			/**
+			 * @deprecated Renamed to {@link OPEN_SIGN_EDITOR}
+			 */
+			@Deprecated
+			public static final PacketType OPEN_SIGN_ENTITY =             OPEN_SIGN_EDITOR.deprecated();
+
 			// ----- Replaced in 1.9.4
 
 			/**