Fix bug with highlight that caused it to update too often

git-svn-id: https://flot.googlecode.com/svn/trunk@280 1e0a6537-2640-0410-bfb7-f154510ff394

jquery.flot.js

@@ -2300,7 +2300,9 @@
                 for (var i = 0; i < highlights.length; ++i) {
                     var h = highlights[i];
                     if (h.auto == eventname &&
-                        !(item && h.series == item.series && h.point == item.datapoint))
+                        !(item && h.series == item.series &&
+                          h.point[0] == item.datapoint[0] &&
+                          h.point[1] == item.datapoint[1]))
                         unhighlight(h.series, h.point);
                 }