Log Message:
Convert to bsd.options.mk, and add three new options: bktr lame vorbis.
The latter two add support for reading/writing mp3 and ogg files,
while the first adds support for grabbing from bktr(4), based on a file
from FreeBSD ports with some additional changes by me.
Additionally, document how to use it in the man page.

Also, add a patch (by me) to use the NetBSD native audio interface instead
of libossaudio (on NetBSD).

Based on PR 24691 and additional mails by Ove Soerensen (thanks!).
Also addresses PR 20281.

Bump PKGREVISION for the audio interface change.