rustdoc: use smarter encoding for playground URL

[notriddle]

The old way would compress okay with DEFLATE, but this version makes uncompressed docs smaller, which matters for memory usage and stuff like cargo doc.

Try it out: https://play.rust-lang.org/?code=fn+main()+{%0Alet+mut+v+=+Vec::new();%0Av.push(1+/+1);%0Aprintln!(%22{}%22,+v[0]);%0A}

In local testing, this change shrinks sample pages by anywhere between 4.0% and 0.031%

$ du -b after.dir/std/vec/struct.Vec.html before.dir/std/vec/struct.Vec.html
759235  after.dir/std/vec/struct.Vec.html
781842  before.dir/std/vec/struct.Vec.html

100*((759235-781842)/781842)=-2.8

$ du -b after.dir/std/num/struct.Wrapping.html before.dir/std/num/struct.Wrapping.html
3194173 after.dir/std/num/struct.Wrapping.html
3204351 before.dir/std/num/struct.Wrapping.html

100*((3194173-3204351)/3204351)=-0.031

$ du -b after.dir/std/keyword.match.html before.dir/std/keyword.match.html
8151    after.dir/std/keyword.match.html
8495    before.dir/std/keyword.match.html

100*((8151-8495)/8495)=-4.0

Gzipped tarball sizes seem shrunk, but not by much.

du -s before.tar.gz after.tar.gz
69600   before.tar.gz
69480   after.tar.gz

100*((69480-69600)/69600)=-0.17

[rustbot]

r? @jsha

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[jsha]

@bors r+ rollup

[bors]

📌 Commit 0db0419 has been approved by jsha

It is now in the queue for this repository.

[notriddle]

CC @matthiaskrgr

Failed in rollup.

@bors r-

[notriddle]

It looks like html5-tidy rejects any url that has things outside the url code points set. I've run it locally, and validated that the fix worked.

@bors r=jsha

[bors]

📌 Commit 51df99f has been approved by jsha

It is now in the queue for this repository.