Add support for leafrefs

Change-Id: I2286aaa96abd960d13bb0b04a778fb264b2f74a4
diff --git a/src/yang_schema.hpp b/src/yang_schema.hpp
index 3621c17..fb4b922 100644
--- a/src/yang_schema.hpp
+++ b/src/yang_schema.hpp
@@ -40,6 +40,7 @@
     bool listHasKey(const schemaPath_& location, const ModuleNodePair& node, const std::string& key) const override;
     const std::set<std::string> listKeys(const schemaPath_& location, const ModuleNodePair& node) const override;
     yang::LeafDataTypes leafType(const schemaPath_& location, const ModuleNodePair& node) const override;
+    yang::LeafDataTypes leafrefBase(const schemaPath_& location, const ModuleNodePair& node) const override;
     const std::set<std::string> validIdentities(const schemaPath_& location, const ModuleNodePair& node, const Prefixes prefixes) const override;
     const std::set<std::string> enumValues(const schemaPath_& location, const ModuleNodePair& node) const override;
     std::set<std::string> childNodes(const schemaPath_& path, const Recursion recursion) const override;