Extend exportfs interface to pass fslocations info into the kernel,
using syntax modelled after AIX. Adds "refer=" and "replicas="
options to /etc/exports to enable use of the kernel fslocation code.
Signed-off-by: Fred Isaman <iisaman@citi.umich.edu> Signed-off-by: Kevin Coffman <kwc@citi.umich.edu> Signed-off-by: Neil Brown <neilb@suse.de>