Remove --enable-brov6 flag, IPv6 now supported by default.

Internally, all BROv6 preprocessor switches were removed and
addr/subnet representations wrapped in the new IPAddr/IPPrefix classes.

Some script-layer changes of note:

- dns_AAAA_reply event signature changed: the string representation
  of an IPv6 addr is easily derived from the addr value, it doesn't
  need to be another parameter.  This event also now generated directly
  by the DNS analyzer instead of being "faked" into a dns_A_reply event.

- removed addr_to_count BIF.  It used to return the host-order
  count representation of IPv4 addresses only.  To make it more
  generic, we might later add a BIF to return a vector of counts
  in order to support IPv6.

- changed the result of enclosing addr variables in vertical pipes
  (e.g. |my_addr|) to return the bit-width of the address type which
  is 128 for IPv6 and 32 for IPv4.  It used to function the same
  way as addr_to_count mentioned above.

- remove bro_has_ipv6 BIF

src/RemoteSerializer.h

@@ -32,7 +32,7 @@ public:
 	static const PeerID PEER_NONE = SOURCE_LOCAL;
 
 	// Connect to host (returns PEER_NONE on error).
-	PeerID Connect(addr_type ip, uint16 port, const char* our_class, double retry, bool use_ssl);
+	PeerID Connect(const IPAddr& ip, uint16 port, const char* our_class, double retry, bool use_ssl);
 
 	// Close connection to host.
 	bool CloseConnection(PeerID peer);
@@ -60,7 +60,7 @@ public:
 	bool CompleteHandshake(PeerID peer);
 
 	// Start to listen.
-	bool Listen(addr_type ip, uint16 port, bool expect_ssl);
+	bool Listen(const IPAddr& ip, uint16 port, bool expect_ssl);
 
 	// Stop it.
 	bool StopListening();