-New method using netlist to read packets on DVD device by sectors of

-New method using netlist to read packets on DVD device by sectors of
2048 bytes.
-Some modifications in netlist to make it work with DVD.
-Fixed � bug in mpeg_system.c

We use INPUT_READ_ONCE many times in the input code. I think that
we should replace it with a field in input_thread_t to give more
flexibility to modules. I have done it in DVD plugin but it can't work
if input.c is limited by INPUT_READ_ONCE.

The DVD method is slower than input_ps ; but there are things to
improve.
CSS descrambling is broken.