improved super seeding with strict option

docs/manual.rst

@@ -3147,6 +3147,7 @@ that will be sent to the tracker. The user-agent is a good way to identify your
 
 		bool announce_to_all_trackers;
 		bool prefer_udp_trackers;
+		bool strict_super_seeding;
 	};
 
 ``user_agent`` this is the client identification to the tracker.
@@ -3445,6 +3446,10 @@ trackers for the same hostname. Setting this to fails means that the
 trackers' tier is respected and there's no preference of one protocol
 over another.
 
+``strict_super_seeding`` when this is set to true, a piece has to
+have been forwarded to a third peer before another one is handed out.
+This is the traditional definition of super seeding.
+
 pe_settings
 ===========