mediafile: prefer latin-1 encoding for ID3 APIC descriptions. Fixes #899

[lazka]

iTunes has problems with everything but latin-1
Try to use latin-1 if possible and fall back to utf-16.

[sampsyo]

Cool! This seems like a reasonable policy. And as far as I can tell, this is the right thing to do on v2.4, right? There's no sense in preferring UTF-8 on v2.4 and Latin-1 on v2.3?

[lazka]

And as far as I can tell, this is the right thing to do on v2.4, right? There's no sense in preferring UTF-8 on v2.4 and Latin-1 on v2.3?

See #899 (comment)

utf-16 and latin-1 are the only working encodings in both cases.

An alternative strategy would be utf-16 if desc else latin-1 (empty utf-16 doesn't work) but preferring latin-1 seems like a better choice given the problems described in #2264

[gboysko]

This change looks great to me. My only suggestion would be to use the symbolic constants (mutagen.id3.Encoding.UTF-16, etc) instead of the numeric values (0, 1).

[gboysko]

Thanks @lazka. Looks great! I'm eager to try it out as soon as it gets merged!

[sampsyo]

Yes, thank you, @lazka! I've merged the fix.