A wrapper that defers the instantiation of a template C with type parameters Ts in a lambda or let expression.
In the code below, the lambda would ideally be written as lambda<_a,_b,push_back<_a,_b>>, however this fails since push_back expects its first argument to be a list, not a placeholder. Instead, we express it using defer as follows:
Inherits defer_< C, list< Ts... > >.
Inherited by meta::extension::apply< F, integer_sequence< T, Is... > >, meta::extension::apply< F, Ret(Args...)>, and meta::extension::apply< F, T< Ts... > >.