Move frame_type parameter in front of stream_id

This commit moves frame_type parameter of
nghttp2_data_soruce_read_length_callback in front of stream_id
parameter.  The motivation is that other callback is generally put
frame related parameters first.  To make it consistent, we move
frame_type, which is frame ralted parameter, to the left.
Wrap longer lines (> 80)
Use datamax if buffer reallocation failed