MINOR: session: add a streams field to the session struct

This will be used to hold the list of streams belonging to a given session.
diff --git a/src/session.c b/src/session.c
index 4295777..a226559 100644
--- a/src/session.c
+++ b/src/session.c
@@ -56,6 +56,7 @@
 	if (sess) {
 		sess->listener = li;
 		sess->fe = fe;
+		LIST_INIT(&sess->streams);
 		sess->origin = origin;
 		sess->accept_date = date; /* user-visible date for logging */
 		sess->tv_accept   = now;  /* corrected date for internal use */