Enable support for new dvdvideo demuxer

This demuxer was added in version 7.0. This adds dependencies for libdvdnav and libdvdread, though these packages are very small (470K combined) and only depend on glibc. Seems worth enabling considering we have libbluray enabled.

Neither libdvdnav nor libdvdread are set up to provide their .so files, so I didn't update the .so dependencies here.