Rename window_size in nghttp2_stream as remote_window_size.

Fix the bug that connection-level local window is not updated
for the data is the last part of the stream. For the stream
level window may ignore this, connection-level window must
be updated. Also this change fixes the bug that connection-level
window is not updated for the ignored DATA frames.

The max length of header block is not used right now. It will
be used when header continuation is implemented.

To match the -w16 to 65535, which is HTTP/2.0 default initial window
size, decrement 1 from (1 << window_bits).

nghttpx does not perform upgrade if the request has request body.

The previous value 100 is non-standard, and if it is not sent with
SETTINGS, session will be closed with protocol error.

Handle HTTP Upgrade and CONNECT explicitly

Fix segmentation fault if DATA frame is received for the stream
which is already closed.