Now remote and local settings are stored separately.
The initial window size is included in SETTINGS frame, all active stream's
window sizes are now updated.
Removed the initial_window_size member from spdylay_stream because
it is the same as remote_settings's initial window size.
Specified stream_user_data_arg can be retrieved by
spdylay_session_get_stream_user_data() function. The application code can use
this function insde spdylay_on_ctrl_send_callback() and identify stream ID
for the request associated by the stream_user_data.
The sample usage is in examples/spdycat.cc.
