un-anchored :hover issue

This is an extension to work already carried out by hpbuniat.
https://github.com/stubbornella/csslint/issues/116
 However the rule he submitted  did not work correctly and threw parser errors when there was a null before :hover
Thsi basic check below threw a cant read a null from text error.
 div.test :hover{
}

This rule is important because it can cause very severe performance issues in IE7 if :hover is used and un-anchored.

  (bug report about un-anchored hovers in IE7 and IE8)
    https://developers.google.com/speed/docs/best-practices/rendering  
    http://msdn.microsoft.com/en-us/library/ie/cc848866%28v=vs.85%29.aspx