Add 'mach clean'.
layout: Don't crash on floated generated content.

It doesn't construct the float correctly, but at least it doesn't crash
anymore.

Fixes Reddit.

Closes #3287.
Merge pull request #3293 from pcwalton/floated-generated-content-crash

layout: Don't crash on floated generated content.
Implement basic support for display: inline-block.

This still needs a lot of work, but it covers the basic
cases and improves wikipedia while passing all existing tests.

Tweak reftest to deal with linux/travis black background.
build: Update submodules
Merge pull request #3315 from saneyuki/mach

Add 'mach clean'.; r=Manishearth
Merge pull request #3286 from glennw/inline_block

Implement basic support for display: inline-block.
Add support for tables that are floated.
Address review comments
Add more arguments to mach test commands
Merge pull request #3312 from mbrubeck/test-name

Add more arguments to mach test commands. r=jack
Merge pull request #3305 from glennw/float-table

Add support for tables that are floated.
Merge pull request #3317 from pcwalton/update-submodules

build: Update submodules
Don't fail converting invalid UTF8 when fetching JS source. Fixes #3302.
Fix incorrect path to about:failure source.
Stop messing with the case of the attribute name in AttributeHandlers::get_attribute.

This fixes a bug where GetAttributeNS would incorrectly match lower-case
attributes when called with an upper-case argument.
Merge pull request #3323 from Ms2ger/get_attribute

Stop messing with the case of the attribute name in AttributeHandlers::get_attribute; r=Manishearth
Merge pull request #3325 from jdm/jsdecode

Don't fail converting invalid UTF8 when fetching JS source. Fixes #3302.
Reinstate errors for unused variables and imports.
Remove obsolete FIXME comment.