some cleanup

- make comment links always visible again
- put codeblock with line num style into mixins
- use yes/no value for $show-line-num-in-codeblock
- use default mixins file in userstyle.scss
hide give gold in link listing

why the fuck there is give gold link in listing page only on submission
that has been gilded and only if it's front page listing. inside the
subreddit's listing page there's no give gold and no gold icon.