Fix leafTypeName returning names of primitive types

This means describe won't tell me
"example-schema:leaf: string (a string)", but just
"example-schema:leaf: (a string)".

Change-Id: I736bf655f3301a61b76485b15cf123448459047e
diff --git a/src/yang_schema.hpp b/src/yang_schema.hpp
index 2a93b07..a4c0b90 100644
--- a/src/yang_schema.hpp
+++ b/src/yang_schema.hpp
@@ -41,6 +41,7 @@
     const std::set<std::string> listKeys(const schemaPath_& location, const ModuleNodePair& node) const override;
     yang::TypeInfo leafType(const schemaPath_& location, const ModuleNodePair& node) const override;
     yang::TypeInfo leafType(const std::string& path) const override;
+    /** @brief If the leaf type is a typedef, returns the typedef name. */
     std::optional<std::string> leafTypeName(const std::string& path) const override;
     std::string leafrefPath(const std::string& leafrefPath) const override;
     std::set<ModuleNodePair> availableNodes(const boost::variant<dataPath_, schemaPath_, module_>& path, const Recursion recursion) const override;