Use 0x88 as stream id when muxing DTS in program streams.

This is what other open source software uses and what
some hardware players expect.
Tested by trac user iuqbgq9h-1 at yahoo
Merge remote-tracking branch 'cehoyos/master'

* cehoyos/master:
  Use 0x88 as stream id when muxing DTS in program streams.

Merged-by: Michael Niedermayer <michaelni@gmx.at>