Working on merging the v6-addr branch. This is checkpoint, tests don't

pass yet.

Changes:

- Gave IPAddress/IPPrefix methods AsString() so that one doesn't need
  to cast to get a string represenation.

- Val::AsAddr()/AsSubnet() return references rather than pointers. I
  find that more intuitive.

- ODesc/Serializer/SerializationFormat get methods to support
  IPAddress/IPPrefix directly.

- Reformatted the comments in IPAddr.h from /// to /** style.

- Given IPPrefix a Contains() method.

- A bit of cleanup.

src/Desc.h

@@ -6,7 +6,9 @@
 #include <stdio.h>
 #include <list>
 #include <utility>
+
 #include "BroString.h"
+#include "IPAddr.h"
 
 typedef enum {
 	DESC_READABLE,
@@ -68,13 +70,14 @@ public:
 
 	void Add(const char* s, int do_indent=1);
 	void AddN(const char* s, int len)	{ AddBytes(s, len); }
+	void Add(const string& s)	{ AddBytes(s.data(), s.size()); }
 	void Add(int i);
 	void Add(uint32 u);
 	void Add(int64 i);
 	void Add(uint64 u);
 	void Add(double d);
-	void Add(const IPAddr& addr);
-	void Add(const IPPrefix& prefix);
+	void Add(const IPAddr& addr)	{ Add(addr.AsString()); }
+	void Add(const IPPrefix& prefix)	{ Add(prefix.AsString()); }
 
 	// Add s as a counted string.
 	void AddCS(const char* s);