[Qt] Unreviewed. Fix minimal build after r142444.

Patch by Zoltan Arvai <zarvai@inf.u-szeged.hu> on 2013-02-11

* css/CSSValue.cpp:
(WebCore::CSSValue::equals):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@142457 268f45cc-cd09-0410-ab3c-d52691b4dbfc