Fix for bug 17254, nth-* selectors do not work with negative coefficients.

        Reviewed by Mitz.

        fast/css/negative-nth-child.html

        * css/CSSStyleSelector.cpp:
        (WebCore::parseNth):

LayoutTests:

        Added test for bug 17254.

        Reviewed by Mitz.

        * fast/css/negative-nth-child.html: Added.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@30116 268f45cc-cd09-0410-ab3c-d52691b4dbfc