REORG: session: move the session parts out of stream.c

This concerns everythins related to accepting a new session and
expiring the embryonic session. There's still a hard-coded call
to stream_accept_session() which could be set somewhere in the
frontend, but for now it's not a problem.
diff --git a/include/proto/session.h b/include/proto/session.h
index 6d45d58..3f008e1 100644
--- a/include/proto/session.h
+++ b/include/proto/session.h
@@ -35,6 +35,7 @@
 extern struct pool_head *pool2_session;
 void session_free(struct session *sess);
 int init_session();
+int session_accept_fd(struct listener *l, int cfd, struct sockaddr_storage *addr);
 
 /* Remove the refcount from the session to the tracked counters, and clear the
  * pointer to ensure this is only performed once. The caller is responsible for
diff --git a/include/proto/stream.h b/include/proto/stream.h
index f8eba12..02992fd 100644
--- a/include/proto/stream.h
+++ b/include/proto/stream.h
@@ -36,7 +36,7 @@
 
 extern struct data_cb sess_conn_cb;
 
-int stream_accept(struct listener *l, int cfd, struct sockaddr_storage *addr);
+int stream_accept_session(struct session *sess, struct task *t);
 
 /* perform minimal intializations, report 0 in case of error, 1 if OK. */
 int init_stream();