xfsprogs-dev: Richacl support

[Andreas Gruenbacher]

Hello,

could the richacl feature flag please be added to xfsprogs so that we
won't end up with incompatible file systems?

  https://github.com/andreas-gruenbacher/xfsprogs-dev

Also, should this really be an incompatible feature flag? Mounting a
richacl filesystem on a kernel without richacl support would otherwise
work but it could grant unwanted access to files.

Thanks,
Andreas