Bump rust-selectors

[emilio]

Depends on servo/rust-selectors#65.

I kept the commits splitted in order to simplify reviewing them, but they should arguably be squashed (the intermediate ones are broken builds).

[highfive]

Heads up! This PR modifies the following files:

• @bholley: components/style/selector_matching.rs, components/style/matching.rs, components/style/lib.rs, components/style/restyle_hints.rs, components/style/element_state.rs, components/style/dom.rs, components/style/stylesheets.rs, components/style/selector_impl.rs

[highfive]

Warning

• These commits modify unsafe code. Please review it carefully!
• These commits modify style, layout, and script code, but no tests are modified. Please consider adding a test!

[emilio]

r? @SimonSapin

[SimonSapin]

Please squash so that each commit compiles. (In this case this maybe everything in one commit.) r=me with that

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Reviewed 1 of 1 files at r1, 5 of 5 files at r2, 6 of 6 files at r3, 15 of 15 files at r4, 3 of 3 files at r5.
Review status: all files reviewed at latest revision, all discussions resolved, some commit checks failed.

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Comments from the review on Reviewable.io

[SimonSapin]

Also ./mach test-tidy reports some errors: https://travis-ci.org/servo/servo/jobs/105528079

[emilio]

Hrrmm...

Happened to me locally right now, but I thought it was just some corruption of the cargo directory or similar:

unable to get packages from source
Caused by:
  Failed to unpack package `selectors v0.4.0`
Caused by:
  No such file or directory (os error 2)

[emilio]

For the record:

This is failing because of rust-lang/cargo#2326, so we're either blocked by the cargoup or by another rust-selector's release.

[nox]

Superseded by #9510.