filehandle: Port to AVIO

This handles all Windows ugliness itself, and allows for remote files
to be used with the libavformat demuxer.

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
init: Initialize the network stack in lavf

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
Style fixes