.caret is smaller in Firefox than other browsers

Created by: vsn4ik

Before and after: http://jsbin.com/daguhewoka/2/edit?html,css,output.

For fix change solid to dashed in https://github.com/twbs/bootstrap/blob/master/less/dropdowns.less#L13.

I believe that it is necessary to add a comment: // dashed: fix caret size for Mozilla Firefox.