They are missing from soundcard.h and are in fact used by some
applications, such as OSS' ossinfo(1):
http://manuals.opensound.com/developer/ossinfo.c.html
The new size for filler is chosen according to the most recent official
version of soundcard.h, which includes those 2 fields. However, the most
recent versions of OSS have renamed "real_device" to "legacy_device",
but for now I chose "real_device" to follow with the rest of the naming
convention we currently have, but this will be changed once the most
recent soundcard.h is ported to FreeBSD.
Sponsored by: The FreeBSD Foundation
MFC after: 1 week