Combine the cover art whitelist with the extensions in
--cover-art-auto-exts instead of hardcoding them. This is shorter,
checks for more extensions, saves us from updating the whitelist
everytime we add a new image extension, and since the whitelist had
gotten so big and the priority is calculated as
MP_ARRAY_SIZE(cover_files) - n, files like cover.jpg were taking
priority over cover art loaded by --cover-art-auto=exact.
Guido Cella
0070a5820e