Macro variadic_generics::va_expand_more_with_nil

macro_rules! va_expand_more_with_nil {
    ($($tt : tt) +) => { ... };
}

Like va_expand, but uses va_invoke_more_with_nil.

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NOTE $va_idents and $va_indices can be empty, so unlike va_expand or va_expand_more, you are required to use zero-or-more repetitions here ($()*).