Associate an object of type T with an execution context's executor.

template<
    typename ExecutionContext,
    typename T>
executor_wrapper< typename decay< T >::type, typename ExecutionContext::executor_type > wrap(
    ExecutionContext & ctx,
    T && t,
    typename enable_if< is_convertible< ExecutionContext &, execution_context & >::value >::type *  = 0);