NOTIFY payload patch

Here is a trivial patch to add support for NOTIFY payloads in 9.0b4:

(tg2env)[15:33:32][agentm@RD07:~/Dev/psycopg2]> git diff
diff --git a/psycopg/connection_int.c b/psycopg/connection_int.c
index 902fdbb..7177e75 100644
--- a/psycopg/connection_int.c
+++ b/psycopg/connection_int.c
@@ -141,9 +141,10 @@ conn_notifies_process(connectionObject *self)
         Dprintf("conn_notifies_process: got NOTIFY from pid %d, msg = %s",
                 (int) pgn->be_pid, pgn->relname);
 
-        notify = PyTuple_New(2);
+        notify = PyTuple_New(3);
         PyTuple_SET_ITEM(notify, 0, PyInt_FromLong((long)pgn->be_pid));
         PyTuple_SET_ITEM(notify, 1, PyString_FromString(pgn->relname));
+       PyTuple_SET_ITEM(notify, 2, PyString_FromString(pgn->extra));
         PyList_Append(self->notifies, notify);
         Py_DECREF(notify);
         PQfreemem(pgn);

Note that this will break code which unpacks the tuple in an assignment:

(pid,name)  = dbconn.notifies.pop()

must become

(pid,name,payload) = dbconn.notifies.pop()

but as long as pop() doesn't return a Notification object, I don't see a way around this.

This patch was tested successfully against 8.4 and 9.0b4 libpq against a 9.0b4 server with an without payloads passed.

Cheers,
M