Remove ol.control.Control.bindMouseOutFocusOutBlur function

It was a workaround added in #1761 to hide the button tooltip on
OSX / Chrome 32 and 33.

Because we're not using the tooltips anymore (see #2781) and this
version of chrome is deprecated this workaround can be removed.

src/ol/control/zoomcontrol.js

@@ -50,8 +50,6 @@ ol.control.Zoom = function(opt_options) {
       goog.events.EventType.CLICK, goog.partial(
           ol.control.Zoom.prototype.handleClick_, delta), false, this);
 
-  ol.control.Control.bindMouseOutFocusOutBlur(inElement);
-
   var outElement = goog.dom.createDom(goog.dom.TagName.BUTTON, {
     'class': className + '-out',
     'type' : 'button',