Change ADTs to generate a copy_construct() that returns this, which should be our new default. Fix storing functions in vectors (lots of bugs here, with funciton types in templates, sizeof, returned by ref, etc. might have missed a few more, put in some warning comments

stdlib/c_generator.krak

@@ -446,7 +446,7 @@ obj c_generator (Object) {
         return str("impossible type") + indirection
     }
     fun type_decoration(type: *type): str {
-        return cify_name(type_to_c(type))
+        return cify_name(type->to_string())
     }
     fun get_name(node: *ast_node): str {
         var maybe_it = ast_name_map.get_ptr_or_null(node);