Fix the check for supports_pending_changesets

supports_pending_changesets is only defined in SCMTool, not Repository.

Reviewed at http://reviews.reviewboard.org/r/4276/
Move .clearfix to defs.less

clearfix is generic code, and should really be in defs, so we can use it from
everywhere.

Reviewed at http://reviews.reviewboard.org/r/4277/