Use f_frsize instead of buf.f_bsize, if available, in os_free_space (for FreeBSD)
Use f_frsize instead of buf.f_bsize, if available, in os_free_space (for FreeBSD)

uroni/urbackup_backend,uroni/urbackup_backend,uroni/urbackup_backend,uroni/urbackup_backend,uroni/urbackup_backend,uroni/urbackup_backend,uroni/urbackup_backend