Factoring out packet decoder from Switch to put that object on a little bit of a diet. Work in progress, wont build yet.

node/Packet.hpp

@@ -562,6 +562,18 @@ public:
 		setVerb(v);
 	}
 
+	/**
+	 * Generate a new IV / packet ID in place
+	 *
+	 * This can be used to re-use a packet buffer multiple times to send
+	 * technically different but otherwise identical copies of the same
+	 * packet.
+	 */
+	inline void newInitializationVector()
+	{
+		Utils::getSecureRandom(field(ZT_PACKET_IDX_IV,8),8);
+	}
+
 	/**
 	 * Set this packet's destination
 	 *