Add Teredo tunnel decapsulation.

Also fix header truncation check for IPv6 No Next header and add an
"ipv6_no_next" weird for such packets that aren't tunneled over Teredo
(which it calls "bubbles" and are used to create mappings in NATs).

src/AYIYA.h

@@ -16,14 +16,13 @@ public:
 		{ return new AYIYA_Analyzer(conn); }
 
 	static bool Available()
+		// TODO: specific option to turn off AYIYA analysis
 		{ return BifConst::Tunnel::max_depth > 0; }
 
 protected:
 	friend class AnalyzerTimer;
 	void ExpireTimer(double t);
 
-	int did_session_done;
-
 	binpac::AYIYA::AYIYA_Conn* interp;
 };