Add cpp_type_alias

src/cpp_namespace.cpp

@@ -18,6 +18,16 @@ bool detail::cpp_namespace_ref_predicate::operator()(const cpp_entity& e)
     return e.kind() == cpp_entity_kind::namespace_t;
 }
 
+std::unique_ptr<cpp_namespace_alias> cpp_namespace_alias::build(const cpp_entity_index& idx,
+                                                                cpp_entity_id id, std::string name,
+                                                                cpp_namespace_ref target)
+{
+    auto ptr = std::unique_ptr<cpp_namespace_alias>(
+        new cpp_namespace_alias(std::move(name), std::move(target)));
+    idx.register_entity(std::move(id), type_safe::ref(*ptr));
+    return ptr;
+}
+
 cpp_entity_kind cpp_namespace_alias::do_get_entity_kind() const noexcept
 {
     return cpp_entity_kind::namespace_alias_t;