ofproto-dpif: Add recirc_id field to struct rule_dpif

ofproto-dpif: Add recirc_id field to struct rule_dpif

This is to allow a recirculation id to be associated with a rule
in the case that its actions cause recirculation.

In such a case if the recirc_id field is non-zero then that value should be
used, otherwise a value should be obtained using
ofproto_dpif_alloc_recirc_id and saved in recirc_id field.

When destructing the rule if the recirc_id field is non-zero then
the associated internal flow should be deleted.

This is in preparation for using the same helper as part of support
for using recirculation in conjunction series of actions including
with MPLS actions that are currently not able to be translated.

Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Ben Pfaff <blp@nicira.com>