compile:
    [javac] Compiling 931 source files to /home/l2dev/updates/nextupdate/gs1900/L2J-C4-SL/build/classes
    [javac] /home/l2dev/updates/nextupdate/gs1900/L2J-C4-SL/java/net/sf/l2j/gameserver/PacketHandler.java:38: cannot find symbol
    [javac] symbol  : class CustomPacketHandlerInterface
    [javac] location: class net.sf.l2j.gameserver.PacketHandler
    [javac]     private static LinkedList<CustomPacketHandlerInterface> customhandlers = new LinkedList<CustomPacketHandlerInterface>();
    [javac]                               ^
    [javac] /home/l2dev/updates/nextupdate/gs1900/L2J-C4-SL/java/net/sf/l2j/gameserver/PacketHandler.java:44: cannot find symbol
    [javac] symbol  : class CustomPacketHandlerInterface
    [javac] location: class net.sf.l2j.gameserver.PacketHandler
    [javac]     public static void addCustomHandler(CustomPacketHandlerInterface handler) {
    [javac]                                             ^
    [javac] /home/l2dev/updates/nextupdate/gs1900/L2J-C4-SL/java/net/sf/l2j/gameserver/PacketHandler.java:48: cannot find symbol
    [javac] symbol  : class CustomPacketHandlerInterface
    [javac] location: class net.sf.l2j.gameserver.PacketHandler
    [javac]     public static void removeCustomHandler(CustomPacketHandlerInterface handler) {
    [javac]                                            ^
    [javac] /home/l2dev/updates/nextupdate/gs1900/L2J-C4-SL/java/net/sf/l2j/gameserver/PacketHandler.java:38: cannot find symbol
    [javac] symbol  : class CustomPacketHandlerInterface
    [javac] location: class net.sf.l2j.gameserver.PacketHandler
    [javac]     private static LinkedList<CustomPacketHandlerInterface> customhandlers = new LinkedList<CustomPacketHandlerInterface>();
    [javac]                                                                                             ^
    [javac] /home/l2dev/updates/nextupdate/gs1900/L2J-C4-SL/java/net/sf/l2j/gameserver/PacketHandler.java:57: cannot find symbol
    [javac] symbol  : class CustomPacketHandlerInterface
    [javac] location: class net.sf.l2j.gameserver.PacketHandler
    [javac]         for (CustomPacketHandlerInterface handler : customhandlers) {
    [javac]              ^
    [javac] Note: Some input files use or override a deprecated API.
    [javac] Note: Recompile with -Xlint:deprecation for details.
    [javac] Note: Some input files use unchecked or unsafe operations.
    [javac] Note: Recompile with -Xlint:unchecked for details.
    [javac] 5 errors