MINOR: session: add a pointer to the session's origin

A session's origin is the entity that was responsible for creating
the session. It can be an applet or a connection for now.
diff --git a/src/hlua.c b/src/hlua.c
index 2934054..363c09b 100644
--- a/src/hlua.c
+++ b/src/hlua.c
@@ -2197,6 +2197,8 @@
 		goto out_fail_conn1;
 	appctx->ctx.hlua.socket = socket;
 	appctx->ctx.hlua.connected = 0;
+	socket->s->sess->origin = &appctx->obj_type;
+
 	LIST_INIT(&appctx->ctx.hlua.wake_on_write);
 	LIST_INIT(&appctx->ctx.hlua.wake_on_read);