Remove allocations in impl Display for Ipv6Addr

[SimonSapin]

No description provided.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @brson (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

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[brson]

@bors r+

[bors]

📌 Commit 31646e1 has been approved by brson

[bors]

⌛ Testing commit 31646e1 with merge 38dac85...

[bors]

💔 Test failed - auto-mac-64-nopt-t

[SimonSapin]

Amended to remove now-unused use prelude::v1::*;.

[alexcrichton]

@bors: r=brson 507d8ca

[bors]

⌛ Testing commit 507d8ca with merge 9f715e9...

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-debug-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-x-android-t, auto-linux-cross-opt, auto-linux-musl-64-opt, auto-mac-32-opt, auto-mac-64-nopt-t, auto-mac-64-opt, auto-win-gnu-32-nopt-t, auto-win-gnu-32-opt, auto-win-gnu-64-nopt-t, auto-win-gnu-64-opt, auto-win-msvc-32-opt, auto-win-msvc-64-opt