Add address sets

An address set is a subset of IP addresses in a CIDR subnet range.
It is built on top of the libcidr library.

Signed-off-by: Jim Lieb <jlieb@panasas.com>
Signed-off-by: Philippe DENIEL <philippe.deniel@cea.fr>
Use address sets in exports and export clients WIP

Signed-off-by: Jim Lieb <jlieb@panasas.com>
Signed-off-by: Philippe DENIEL <philippe.deniel@cea.fr>
Update mnt_export to use address sets WIP

Signed-off-by: Jim Lieb <jlieb@panasas.com>
Signed-off-by: Philippe DENIEL <philippe.deniel@cea.fr>
squash use address bits in export

we have to refactor the add_client to consolidate client ips where we can
subnet is done but the rest are still one offs.

Signed-off-by: Jim Lieb <jlieb@panasas.com>
Signed-off-by: Philippe DENIEL <philippe.deniel@cea.fr>
CIDR: integration of fresh code from libcidr. Now supports IPv6.

Signed-off-by: Philippe DENIEL <philippe.deniel@cea.fr>