Add support for leafrefs

Change-Id: I2286aaa96abd960d13bb0b04a778fb264b2f74a4
diff --git a/src/schema.hpp b/src/schema.hpp
index 64f743c..e0d30af 100644
--- a/src/schema.hpp
+++ b/src/schema.hpp
@@ -33,6 +33,7 @@
     Enum,
     Binary,
     IdentityRef,
+    LeafRef,
 };
 }
 
@@ -73,6 +74,8 @@
     virtual bool listHasKey(const schemaPath_& location, const ModuleNodePair& node, const std::string& key) const = 0;
     virtual const std::set<std::string> listKeys(const schemaPath_& location, const ModuleNodePair& node) const = 0;
     virtual yang::LeafDataTypes leafType(const schemaPath_& location, const ModuleNodePair& node) const = 0;
+    virtual yang::LeafDataTypes leafrefBase(const schemaPath_& location, const ModuleNodePair& node) const = 0;
+
     virtual const std::set<std::string> validIdentities(const schemaPath_& location, const ModuleNodePair& node, const Prefixes prefixes) const = 0;
     virtual const std::set<std::string> enumValues(const schemaPath_& location, const ModuleNodePair& node) const = 0;
     virtual std::set<std::string> childNodes(const schemaPath_& path, const Recursion recursion) const = 0;