CLEANUP: connection: remove unused server/proxy/task/si_applet declarations
These ones are left-overs from the code before the introduction of
obj_type.
diff --git a/include/types/connection.h b/include/types/connection.h
index 85ea48c..b2396c4 100644
--- a/include/types/connection.h
+++ b/include/types/connection.h
@@ -35,10 +35,6 @@
struct connection;
struct buffer;
struct pipe;
-struct server;
-struct proxy;
-struct si_applet;
-struct task;
/* Polling flags that are manipulated by I/O callbacks and handshake callbacks
* indicate what they expect from a file descriptor at each layer. For each