Update UA stylesheets for lists

[recrack]

#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

[hoppipolla-critic-bot]

Critic review: https://critic.hoppipolla.co.uk/r/544

This is an external review system which you may optionally use for the code review of your pull request.

In order to help critic track your changes, please do not make in-place history rewrites (e.g. via git rebase -i or git commit --amend) when updating this pull request.

[SimonSapin]

Eventually I wish we could base our UA stylesheet on the Rendering section of the spec, but unfortunately so much of it is written in prose rather than CSS. Maybe we could still express that prose in CSS with additional internal-only keywords, or something.

In the meantime, this looks fine. This is adding style for the obsolete <multicol> element, but that shouldn’t be harmful.

[recrack]

@SimonSapin Thanks. This reference site is very helpful for me. (http://www.whatwg.org/specs/web-apps/current-work/multipage/rendering.html)