Loxigen: added src/dst meta id matches

Encode a 1 byte src and 1 byte dst 'meta' ID into
ofp_match's pad2 byte.
diff --git a/loxi_front_end/match.py b/loxi_front_end/match.py
index 42c0a9e..5c83859 100644
--- a/loxi_front_end/match.py
+++ b/loxi_front_end/match.py
@@ -394,6 +394,28 @@
         takes_mask_in_spec=False,
         order=501,
         ),
+
+    src_meta_id = dict(
+        name="src_meta_id",
+        m_type="uint8_t",
+        v1_wc_shift=23,
+        v2_wc_shift=23,
+        print_type="PRIx8",
+        conditions="",
+        takes_mask_in_spec=False,
+        order=600,
+        ),
+
+    dst_meta_id = dict(
+        name="dst_meta_id",
+        m_type="uint8_t",
+        v1_wc_shift=24,
+        v2_wc_shift=24,
+        print_type="PRIx8",
+        conditions="",
+        takes_mask_in_spec=False,
+        order=601,
+        ),
 )
 
 match_keys_sorted = of_match_members.keys()
@@ -411,7 +433,9 @@
     "tcp_dst",  # Means UDP too for 1.0 and 1.1
     "tcp_src",  # Means UDP too for 1.0 and 1.1
     "vlan_pcp",
-    "vlan_vid"
+    "vlan_vid",
+    "src_meta_id",
+    "dst_meta_id",
     ]
 
 of_v2_keys = [