Add parser support for bits

Change-Id: I8f36a2639d3f4911c2fb825dd3bf28956886a9a6
diff --git a/src/leaf_data_type.hpp b/src/leaf_data_type.hpp
index 288f765..98cb12e 100644
--- a/src/leaf_data_type.hpp
+++ b/src/leaf_data_type.hpp
@@ -65,6 +65,10 @@
     bool operator==(const IdentityRef& other) const;
     std::set<identityRef_> m_allowedValues;
 };
+struct Bits {
+    bool operator==(const Bits& other) const;
+    std::set<std::string> m_allowedValues;
+};
 struct LeafRef;
 struct Union;
 using LeafDataType = std::variant<
@@ -83,6 +87,7 @@
     yang::Binary,
     yang::Empty,
     yang::IdentityRef,
+    yang::Bits,
     yang::LeafRef,
     yang::Union
 >;