Add support for identityref data type

Change-Id: I369150b83d86a4c22fadf383ee011eee619a4c15
diff --git a/src/ast_commands.hpp b/src/ast_commands.hpp
index 5015787..f4cd0a9 100644
--- a/src/ast_commands.hpp
+++ b/src/ast_commands.hpp
@@ -198,6 +198,7 @@
 BOOST_FUSION_ADAPT_STRUCT(set_, m_path, m_data)
 BOOST_FUSION_ADAPT_STRUCT(enum_, m_value)
 BOOST_FUSION_ADAPT_STRUCT(binary_, m_value)
+BOOST_FUSION_ADAPT_STRUCT(identityRef_, m_prefix, m_value)
 BOOST_FUSION_ADAPT_STRUCT(commit_)
 BOOST_FUSION_ADAPT_STRUCT(help_, m_cmd)
 BOOST_FUSION_ADAPT_STRUCT(discard_)