Allow tagging AAC/ADTS files with APEv2 tags

from http://bugs.musicbrainz.org/ticket/3239

I've got a bunch of PsyTEL FastAAC files and they are odd to me. First, they use extension .aac insted of .m4a, but that's not a problem, since extension doesn't mean a thing generally, only it matters to Picard sometimes. Secondly they are reported as being:
MPEG ADTS, AAC, v2 LC
instead of
ISO Media, MPEG v4 system, iTunes AAC-LC
for example. But the most odd thing is they are using APEv2 tags.

Of course I cannot tag them with Picard. Of course I'd like to.