Add missing stream callback functionality

Investigating a Debian bug report https://bugs.debian.org1020452 I decided to test every codepath of DVD playback: VIDEO_TS/VIDEO_TS.IFO, videotest.iso and http://x.x.x.x/videotest.iso. I did not install libdvdcss as it is not present in Debian repositories for legal concerns. I found that the code binding stream callbacks to libdvdread was moved long ago when libdvdcss was split.

This bug largely went unnoticed because most people likely have followed the steps to compile libdvdcss as mentioned on (outdated) Debian wiki page.

I restored the code and tested it by playing videotest iso. Without this patch, video playback failed, with it it played.

Steps to reproduce:

1. Install Kodi from Debian official repositories: apt-get update && apt-get install kodi kodi-eventclients-kodi-send
2. Download http://www.deniscarl.com/dvdtest/videotest.zip and unpack it to /tmp
3. Start playback of /tmp/videotest.iso: kodi-send --action='PlayMedia(/tmp/videotest.iso)'
4. Enjoy the playback failure message ;)

@jbk is it possible to merge this before we get to videolan/libdvdread#40 ? We need that PRs upstream because of Kodi bugs.

If you want I will provide a docker-compose file to rapidly deploy the test environment for you!