TDL [codegen]: added basic structure

lib/codegen.cpp

@@ -0,0 +1,14 @@
+#include "codegen.h"
+#include "ast.h"
+
+namespace tdl{
+
+namespace ast{
+
+void translation_unit::codegen(module *mod)
+{ decls_->codegen(mod); }
+
+
+}
+
+}