Improve handling of IPv6 routing type 0 extension headers.

- flow_weird event with name argument value of "routing0_hdr" is raised
  for packets containing an IPv6 routing type 0 header because this
  type of header is now deprecated according to RFC 5095.

- packets with a routing type 0 header and non-zero segments left
  now use the last address in that header in order to associate
  with a connection/flow and for calculating TCP/UDP checksums.

- added a set of IPv4/IPv6 TCP/UDP checksum unit tests

src/EventHandler.h

@@ -7,7 +7,6 @@
 
 #include "List.h"
 #include "BroList.h"
-#include "net_util.h"
 
 class Func;
 class FuncType;