Update less.js to 1.3.3 re-release

Fixes https://github.com/cloudhead/less.js/issues/1095
See https://github.com/cloudhead/less.js/commit/c06d8498777f5042e161d5d21d1972854330518f
Merge pull request #1213 from wmono/master

Update less.js to 1.3.3 re-release