Return 'BackCompat' for document.compatMode only if in quirksmode
Mark linebreak_simple_a.html as flaky on cpu reftests.

It has failed on three unrelated PRs:

https://s3.amazonaws.com/archive.travis-ci.org/jobs/31574326/log.txt
https://s3.amazonaws.com/archive.travis-ci.org/jobs/31581185/log.txt
https://s3.amazonaws.com/archive.travis-ci.org/jobs/31592052/log.txt
Merge pull request #2997 from Ms2ger/flaky-reftest

Mark linebreak_simple_a.html ass flaky on cpu reftests; r=SimonSapin
Use TaskBuilder to spawn worker threads.
Use TaskBuilder for the main Servo task.
Merge pull request #2996 from hazz/document-compatmode

Return 'BackCompat' for document.compatMode only if in quirksmode; r=Ms2ger
remove unnecessary clone usage
Un-blacklist the layout crate from rustdoc. See #2924.

Whatever rustdoc bug we used to hit was solved by the Rust upgrade.
(The style crate still causes rustdoc to overflow its stack.)

Also use Markdown tables rather than ASCII diagrams in inlines.rs.
Not only does this look nicer, this works around rustdoc trying
(and failing) to parse them as Rust code.
Move documentation table stylining to a shared location.
Blacklisted docs don’t need any dependency, since we don’t actually generate them.
Merge pull request #3001 from jxs/master

remove unnecessary clone usage
Merge pull request #2998 from Ms2ger/taskbuilder

Use TaskBuilder where possible; r=metajack
Merge pull request #3002 from servo/rustdoc-layout

Un-blacklist the layout crate from rustdoc.
Fix rustdoc comment syntax in gfx::display_list.
Merge pull request #3004 from mbrubeck/doc-comment

Fix rustdoc comment syntax in gfx::display_list. r=zwarich