Update UA stylesheets for lists
Upgrade to latest Rust.
auto merge of #1473 : metajack/servo/rustup-20131219, r=jdm
auto merge of #1478 : recrack/servo/useragentcss, r=SimonSapin

#1232

Servo UA (http://www.w3.org/TR/CSS21/sample.html)

This is UA css from http://mxr.mozilla.org/mozilla/source/layout/style/html.css and http://dev.w3.org/csswg/css-lists/#ua-stylesheet

```
ul margin-left: 40px -> padding-left: 40px
ol margin-left: 40px -> padding-left: 40px
```
Remove needless code.

This `OK(())` should be propagated from `Element.set_attribute()`.
Split up the utility function to make internal attribute's namespace.
Enable only remove operation for Document::update_idmap().
Add the comment to explain the dual declaration.
Implement Element.removeAttribute()/removeAttributeNS().
auto merge of #1448 : saneyuki/servo/attr, r=jdm