Fixed problem with bar highlights (report by Chris Leonello)

git-svn-id: https://flot.googlecode.com/svn/trunk@134 1e0a6537-2640-0410-bfb7-f154510ff394

jquery.flot.js

@@ -1392,7 +1392,7 @@
                 c.lineTo(left, top);
                 c.lineTo(right, top);
                 c.lineTo(right, bottom);
-                ctx.fillStyle = fillStyleCallback(bottom, top);
+                c.fillStyle = fillStyleCallback(bottom, top);
                 c.fill();
             }