BUG(2567): use libdiscid read_sparse()

discid_read() fetches ISRCs and the MCN starting with libdiscid 0.3.1,
which takes a couple of seconds.
Starting with libdiscid 0.5.0 discid_read_sparse() is available,
which only reads the TOC, unless requested otherwise.

When read_sparse() is not available, we keep using read().
OTHER: Add Johannes Dewender to AUTHORS.
OTHER: Cut the last weird header dependency in the cli.