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

As discussed in the issue tracker for the wg-allocators working group[1], updating this implementation for allocator support was most likely just forgotten in the original PR.

[1]: https://github.com/rust-lang/wg-allocators/issues/86

aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust