The stream code does not access many option variables directly, but it
does access some such as audio_id and network_bandwidth (and does that
without including proper headers for them). Add option pointer to the
stream struct to allow access to those variables. Remove the unused
(always NULL) and clumsy-looking char** options parameter in the
open_stream call and replace it with the option pointer. The parameter
is currently only set in the main open_stream() call in MPlayer.c and
not in any other locations that can open a stream.
In the long term it might be better to pass a more limited set of
values somehow, but this should do for now.
