twbs/bootstrap — pull request #9856 by wangsai (2013-08-19 16:24:41+00:00)
Title: `.clearfix` defined in `utilities.less` will cause duplicated code in css file

`.clearfix` defined in `utilities.less` will cause duplicated code to css file when call `.clearfix()`.It may be a circular reference.

So, changing `.clearfix` in `utilities.less` to `.clear-fix` will resolve this bug.

And ,it may be a bug of less.