Fix. Thanks to zzz @ #i2p-dev

Background (IRC Log):
13:52 < zzz> Meeh, I got a i2pd patch for you
13:52 < zzz> ssu.h line 29 change comment '3 bits' back to '4 bits' and below add 
             PAYLOAD_TYPE_SESSION_DESTROYED = 8
13:53 < zzz> he missed it in the copypasta from our UDPPacket.java
13:54 < zzz>     /** @since 0.8.1 */
13:54 < zzz>     public static final int PAYLOAD_TYPE_SESSION_DESTROY = 8;