Generalize the Write impl for `Vec<u8>` to `Vec<u8, A>`

[athre0z]

I'd like to generalize the Write impl for Vec<u8> to Vec<u8, A>. Is there any reason for not doing this? I suspect that this impl might simply have been forgotten because it lives in the io module rather than by the other trait impls for Vec?

[TimDiekmann]

Please go ahead, I think I simply forgot to implement it. 🙂

[athre0z]

Excellent — I created a PR over at rust-lang/rust#82862!

[athre0z]

Aaaand it's merged! I'd like to use this chance to thank you (and everyone else involved with this!) for your work on allocator_api. I think that this gets a lot less attention than it deserves. Particularly for gracefully working with arena allocators, this is super important to have!

[ChayimFriedman2]

I think we need to check if we have other forgotten impls. A simple way will be to just remove the default type for A and search for compiler errors.