New upstream release 1.6.3
    
    - https://github.com/less/less.js/blob/v1.6.3/CHANGELOG.md
    - Fix issue with calling toCSS twice not working in some situations (like with
      bootstrap 2)
    - The Rhino release is fixed!
    - ability to use uppercase colours
    - Fix a nasty bug causing syntax errors when selector interpolation is preceded
      by a long comment (and some other cases)
    - Fix a major bug with the variable scope in guards on selectors (e.g. not
      mixins)
    - Fold in & when () { to the current selector rather than duplicating it
    - fix another issue with array prototypes
    - add a url-args option which adds a value to all urls (for cache busting)
    - Round numbers to 8 decimal places - thereby stopping javascript precision
      errors
    - some improvements to the default() function in more complex scenarios
    - improved missing '{' and '(' detection