vectored, all and advance_slices

[FrankReh]

Will there be more in the future about write_vectored, write_all_vectored and advance_slices?

There is the Tracking issue for io_slice_advance that shows the progress towards getting such an advance feature into std because write_vectored is important to networking people and how an advance_slices implementation greatly simplifies their code and improves the performance of their code. (Well, the last part of that statement might be a little loaded but hopefully one gets the point by reading through the comments.)

[nrc]

Yeah, I think it is future work which we should definitely do