Add documentation about web-platform-tests.
Merge pull request #3150 from Ms2ger/wpt-docs

Add documentation about web-platform-tests; r=jgraham
Load bare images within an HTML document (#3108)
Update ProxyTraps to use real bools.
Merge pull request #3151 from Ms2ger/bools

Update ProxyTraps to use real bools; r=jdm
Merge pull request #3131 from Manishearth/image

Load bare images within an HTML document (#3108); r=Ms2ger
Add missing clean-* make targets.

Some more recent Servo crates were not cleaned by `make servo-clean`.
Nuke Node's TLayoutData

LayoutData{Ref} structs replaced its usage for quite some time now.
Correct capitalization of "libXrandr-devel" in Fedora prerequisites list.
Merge pull request #3155 from brunoabinader/nuke-tlayoutdata

Nuke Node's TLayoutData; r=jdm
Merge pull request #3158 from sstangl/master

Correct capitalization of "libXrandr-devel" in Fedora prerequisites list...
Merge pull request #3152 from SimonSapin/clean

Add missing clean-* make targets.