Fix bug that connection window is consumed excessively

Previously we consider bytes as consumed in spdylay_session_mem_recv()
even if it is not ignored and is passing to application.  As a result,
excessive number of bytes are considered as consumed and library sends
excessive amount of WINDOW_UPDATE to peer.  This commit fixes this
bug.

lib/spdylay_session.c

@@ -2827,7 +2827,8 @@ ssize_t spdylay_session_mem_recv(spdylay_session *session,
             return r;
           }
 
-          if(session->opt_flags & SPDYLAY_OPTMASK_NO_AUTO_WINDOW_UPDATE2) {
+          if(session->iframe.state == SPDYLAY_RECV_PAYLOAD_IGN &&
+             (session->opt_flags & SPDYLAY_OPTMASK_NO_AUTO_WINDOW_UPDATE2)) {
             r = spdylay_session_update_connection_consumed_size
               (session, readlen);