280eb2239a io: Remove the impl_write macro (Tobin C. Harding)
Pull request description:
We have found calling macros from other crates to be error prone, especially when they involve feature gates. Furthermore the `impl_write` macro is trivial to write, users can just write it in the crate that needs it.
Lets just remove the macro. While we are at it point users to the examples in `bitcoin/examples/io.rs` for usage of the `io` crate.
Close: #3872
ACKs for top commit:
Kixunil:
ACK 280eb2239a
apoelstra:
ACK 280eb2239a2fcaa83a35ae6fb1ce62fe35a1e222; successfully ran local tests
Tree-SHA512: 62766ff6e4b5f3fae2d6214e87bd90c15b3103248effd4399a070ac831473b0288e599eed2377c08d2b7eca263220f172c8399a607756793477f82d3dc8f1b67