De @-mut windowing.
Use custom enum for the namespace of attribute selectors.

… instead of None meaning "any namespace"
(where it could be the null namespace.)
auto merge of #1661 : SimonSapin/servo/attr-selectors, r=jdm

… instead of None meaning "any namespace" (where it could be the null namespace.)
RefCell->Cell
Glut RefCell->Cell
auto merge of #1663 : larsbergstrom/servo/remove_atmut, r=pcwalton

I'm submitting a part of this at first to get your feedback on whether I'm removing them in the style you like (before I go and push this strategy through the rest of non-script Servo). Note that Windowing is a little weird because its calls bounce down into C code which then re-calls into Rust, getting a handle on the Rc'd Window object out of TLS.

r? @pcwalton
Adding most commonly used parts of window.console. Fixes Issue#506. r=Ms2ger
auto merge of #1666 : ozten/servo/issue-506-add-basic-console, r=Ms2ger

Here is an attempt to fix Issue#506.

I couldn't figure out how to do variadic arguments to `console.log`, but I did test calling `console.log('foo', 'bar', 'baz')` and it prints the first argument and doesn't error out, which is nice.

window.console is not a web standards. I did the popular functions, but not some of the newer ones documented [on MDN](https://developer.mozilla.org/en-US/docs/Web/API/console).

This PR will allow more pages to load properly, where developers have left in window.console calls.
Bumped HTMLCollection interface to latest

Spec:
http://dom.spec.whatwg.org/#interface-htmlcollection

This is a sub-task for #1662.
Added HTMLCollection::create

This is a sub-task for #1662.
s/createHTMLCollection/create_html_collection

This method is part of the internal API.

This is a sub-task for #1662.
Implement Document's getElementsBy{TagName,TagNameNS,ClassName}

Specs:
http://dom.spec.whatwg.org/#dom-document-getelementsbytagname
http://dom.spec.whatwg.org/#dom-document-getelementsbytagnamens
http://dom.spec.whatwg.org/#dom-document-getelementsbyclassname

This is a sub-task for #1662.
Implement Element's getElementsBy{TagName,TagNameNS,ClassName}

Specs:
http://dom.spec.whatwg.org/#dom-document-getelementsbytagname
http://dom.spec.whatwg.org/#dom-document-getelementsbytagnamens
http://dom.spec.whatwg.org/#dom-document-getelementsbyclassname

This is a sub-task for #1662.
Added FIXME stub comments

This is a sub-task for #1662.
Refactor on HTMLCollection to avoid code duplication

Fixes:
 - Replaced eq_slice() calls with Eq-like string comparison;
 - Removed collect() usage - slice() already provides an iterator;
 - Moved getElementsBy{TagName,TagNameNS,ClassName} common code from
   both Document and Element to HTMLCollection;
Cleaned up collect()/eq_slice() usage in Element::has_class