-chapter can optionally take a range with a start and an end. Add a
new option type which supports such values and use that instead of a
custom per-option function.
This commit also fixes a build configuration bug: before the
availability of the -chapter option depended on DVD functionality
being enabled in the binary, even though the option works with other
sources too.
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.