[less.js] clean up comments
[test-less.html] add more less to test
[test-less.html] more LESS to test
add .hljs-color to the stylesheet
[less.js] greatly improve less.MIX_IN mode
[less.js] take steps to improve auto detection
[less.js] fix a bug: allow less variables in css functions
[less.js] extract css selectors to a grouping object (css.selector)
[less.js] add css color keywords