IP Multicast FIB (mfib)

 - IPv[46] mfib tables with support for (*,G/m), (*,G) and (S,G) exact and longest prefix match
 - Replication represented via a new replicate DPO.
 - RPF configuration and data-plane checking
 - data-plane signals sent to listening control planes.

The functions of multicast forwarding entries differ from their unicast conterparts, so we introduce a new mfib_table_t and mfib_entry_t objects. However, we re-use the fib_path_list to resolve and build the entry's output list. the fib_path_list provides the service to construct a replicate DPO for multicast.

'make tests' is added to with two new suites; TEST=mfib, this is invocation of the CLI command 'test mfib' which deals with many path add/remove, flag set/unset scenarios, TEST=ip-mcast, data-plane forwarding tests.

Updated applications to use the new MIFB functions;
  - IPv6 NS/RA.
  - DHCPv6
 unit tests for these are undated accordingly.

Change-Id: I49ec37b01f1b170335a5697541c8fd30e6d3a961
Signed-off-by: Neale Ranns <nranns@cisco.com>
diff --git a/src/vnet/dpo/dpo.h b/src/vnet/dpo/dpo.h
index 1efcbc8..aff4e1b 100644
--- a/src/vnet/dpo/dpo.h
+++ b/src/vnet/dpo/dpo.h
@@ -100,15 +100,18 @@
      * @brief load-balancing over a choice of [un]equal cost paths
      */
     DPO_LOAD_BALANCE,
+    DPO_REPLICATE,
     DPO_ADJACENCY,
     DPO_ADJACENCY_INCOMPLETE,
     DPO_ADJACENCY_MIDCHAIN,
     DPO_ADJACENCY_GLEAN,
+    DPO_ADJACENCY_MCAST,
     DPO_RECEIVE,
     DPO_LOOKUP,
     DPO_LISP_CP,
     DPO_CLASSIFY,
     DPO_MPLS_LABEL,
+    DPO_MFIB_ENTRY,
     DPO_LAST,
 } __attribute__((packed)) dpo_type_t;
 
@@ -123,12 +126,15 @@
     [DPO_ADJACENCY_INCOMPLETE] = "dpo-adjacency-incomplete",	\
     [DPO_ADJACENCY_MIDCHAIN] = "dpo-adjacency-midcahin",	\
     [DPO_ADJACENCY_GLEAN] = "dpo-glean",	\
+    [DPO_ADJACENCY_MCAST] = "dpo-adj-mcast",	\
     [DPO_RECEIVE] = "dpo-receive",	\
     [DPO_LOOKUP] = "dpo-lookup",	\
     [DPO_LOAD_BALANCE] = "dpo-load-balance",	\
+    [DPO_REPLICATE] = "dpo-replicate",	\
     [DPO_LISP_CP] = "dpo-lisp-cp",	\
     [DPO_CLASSIFY] = "dpo-classify",	\
-    [DPO_MPLS_LABEL] = "dpo-mpls-label"	\
+    [DPO_MPLS_LABEL] = "dpo-mpls-label", \
+    [DPO_MFIB_ENTRY] = "dpo-mfib_entry"	\
 }
 
 /**