MINOR: connection: introduce conn_stream

This patch introduces a new struct conn_stream. It's the stream-side of
a multiplexed connection. A pool is created and destroyed on exit. For
now the conn_streams are not used at all.
diff --git a/src/connection.c b/src/connection.c
index b61a9dd..2e081d8 100644
--- a/src/connection.c
+++ b/src/connection.c
@@ -28,6 +28,7 @@
 #endif
 
 struct pool_head *pool2_connection;
+struct pool_head *pool2_connstream;
 struct xprt_ops *registered_xprt[XPRT_ENTRIES] = { NULL, };
 
 /* List head of all known muxes for ALPN */
@@ -39,7 +40,19 @@
 int init_connection()
 {
 	pool2_connection = create_pool("connection", sizeof (struct connection), MEM_F_SHARED);
-	return pool2_connection != NULL;
+	if (!pool2_connection)
+		goto fail_conn;
+
+	pool2_connstream = create_pool("conn_stream", sizeof(struct conn_stream), MEM_F_SHARED);
+	if (!pool2_connstream)
+		goto fail_cs;
+
+	return 1;
+ fail_cs:
+	pool_destroy2(pool2_connection);
+	pool2_connection = NULL;
+ fail_conn:
+	return 0;
 }
 
 /* I/O callback for fd-based connections. It calls the read/write handlers