dump: add IPv6 support

Change-Id: Id9d10cf1080d2d7f98e9a48216c6564c6bbf8607
Refs: #3861
diff --git a/tools/dump/ndndump.hpp b/tools/dump/ndndump.hpp
index 25a35d4..0198026 100644
--- a/tools/dump/ndndump.hpp
+++ b/tools/dump/ndndump.hpp
@@ -76,6 +76,9 @@
   printIp4(OutputFormatter& out, const uint8_t* pkt, size_t len) const;
 
   bool
+  printIp6(OutputFormatter& out, const uint8_t* pkt, size_t len) const;
+
+  bool
   printTcp(OutputFormatter& out, const uint8_t* pkt, size_t len) const;
 
   bool