L2-fwd trace show the lookup result

Change-Id: I09cf6ee7b4874d71f293f8f1a426d3a5e9651749
Signed-off-by: Neale Ranns <nranns@cisco.com>
diff --git a/src/vnet/l2/l2_fib.h b/src/vnet/l2/l2_fib.h
index 626fbe5..d8b37d2 100644
--- a/src/vnet/l2/l2_fib.h
+++ b/src/vnet/l2/l2_fib.h
@@ -129,6 +129,8 @@
 
 STATIC_ASSERT_SIZEOF (l2fib_entry_result_flags_t, 1);
 
+extern u8 *format_l2fib_entry_result_flags (u8 * s, va_list * args);
+
 /*
  * The l2fib entry results
  */