openflow_input: declare of_flowmod.flags as enum ofp_flow_mod_flags

others will follow
diff --git a/openflow_input/standard-1.3 b/openflow_input/standard-1.3
index 119e7a4..e0f08b6 100644
--- a/openflow_input/standard-1.3
+++ b/openflow_input/standard-1.3
@@ -924,7 +924,7 @@
     uint32_t buffer_id;
     of_port_no_t out_port;
     uint32_t out_group;
-    uint16_t flags;
+    ofp_flow_mod_flags flags;
     pad(2);
     of_match_t match;
     list(of_instruction_t) instructions;
@@ -945,7 +945,7 @@
     uint32_t buffer_id;
     of_port_no_t out_port;
     uint32_t out_group;
-    uint16_t flags;
+    ofp_flow_mod_flags flags;
     pad(2);
     of_match_t match;
     list(of_instruction_t) instructions;
@@ -966,7 +966,7 @@
     uint32_t buffer_id;
     of_port_no_t out_port;
     uint32_t out_group;
-    uint16_t flags;
+    ofp_flow_mod_flags flags;
     pad(2);
     of_match_t match;
     list(of_instruction_t) instructions;
@@ -987,7 +987,7 @@
     uint32_t buffer_id;
     of_port_no_t out_port;
     uint32_t out_group;
-    uint16_t flags;
+    ofp_flow_mod_flags flags;
     pad(2);
     of_match_t match;
     list(of_instruction_t) instructions;
@@ -1008,7 +1008,7 @@
     uint32_t buffer_id;
     of_port_no_t out_port;
     uint32_t out_group;
-    uint16_t flags;
+    ofp_flow_mod_flags flags;
     pad(2);
     of_match_t match;
     list(of_instruction_t) instructions;
@@ -1029,7 +1029,7 @@
     uint32_t buffer_id;
     of_port_no_t out_port;
     uint32_t out_group;
-    uint16_t flags;
+    ofp_flow_mod_flags flags;
     pad(2);
     of_match_t match;
     list(of_instruction_t) instructions;