current-filesystem(): accommodate NetBSD and SunOS.
current-filesystem(): accommodate NetBSD and SunOS.

Thanks to Thomas Klausner <tk@giga.or.at> for reporting the problem,
and providing the alternate commands.

Signed-off-by: Rob Browning <1dc5917c2adeeba13d1ef33dbb40691a1b67cc65@defaultvalue.org>

mhoeher/bup,gevaerts/bup,ToxicFrog/bup,jbaber/bup,tjanez/bup,jbaber/bup,mhoeher/bup,mhoeher/bup,gevaerts/bup,pombredanne/bup,mhoeher/bup,jbaber/bup,jbaber/bup,tjanez/bup,ToxicFrog/bup,mhoeher/bup,pombredanne/bup,pombredanne/bup,tjanez/bup,tjanez/bup,tjanez/bup,ToxicFrog/bup,jbaber/bup,pombredanne/bup,mhoeher/bup,pombredanne/bup,tjanez/bup,gevaerts/bup,ToxicFrog/bup,ToxicFrog/bup,gevaerts/bup,pombredanne/bup,gevaerts/bup,jbaber/bup