Add GPRS Tunnelling Protocol (GTPv1) decapsulation.

This currently supports automatic decapsulation of GTP-U packets on
UDP port 2152.

The GTPv1 headers for such tunnels can be inspected by handling the
"gtpv1_g_pdu_packet" event, which has a parameter of type "gtpv1_hdr".

Analyzer and test cases are derived from submissions by Carsten Langer.

Addresses #690.

src/GTPv1.h

@@ -0,0 +1,29 @@
+#ifndef GTPv1_h
+#define GTPv1_h
+
+#include "gtpv1_pac.h"
+
+class GTPv1_Analyzer : public Analyzer {
+public:
+	GTPv1_Analyzer(Connection* conn);
+	virtual ~GTPv1_Analyzer();
+
+	virtual void Done();
+	virtual void DeliverPacket(int len, const u_char* data, bool orig,
+					int seq, const IP_Hdr* ip, int caplen);
+
+	static Analyzer* InstantiateAnalyzer(Connection* conn)
+		{ return new GTPv1_Analyzer(conn); }
+
+	static bool Available()
+		{ return BifConst::Tunnel::enable_gtpv1 &&
+		         BifConst::Tunnel::max_depth > 0; }
+
+protected:
+	friend class AnalyzerTimer;
+	void ExpireTimer(double t);
+
+	binpac::GTPv1::GTPv1_Conn* interp;
+};
+
+#endif