Refactor to make bro use a common Packet object.

Do a better job of parsing layer 2 and keeping track of layer 3 proto.
Add support for raw packet event, including Layer2 headers.

src/Conn.h

@@ -86,9 +86,7 @@ public:
 			const u_char*& data,
 			int& record_packet, int& record_content,
 			// arguments for reproducing packets
-			const struct pcap_pkthdr* hdr,
-			const u_char* const pkt,
-			int hdr_size);
+			const Packet *pkt);
 
 	HashKey* Key() const			{ return key; }
 	void ClearKey()				{ key = 0; }