Datepicker: only set the focus explicitly if it is not already on the target field. Fixed #6694 – datepicker does not fire change event in IE8

jQuery stores the current content of a field whenever it gets the focus. Since the fixed function is also called for KeyUp events the change event is not triggered anymore when the input looses focus.
(cherry picked from commit 39cf7d5)

Author: tobiasbrunner

ui/jquery.ui.datepicker.js

@@ -700,7 +700,9 @@ $.extend(Datepicker.prototype, {
 		inst.dpDiv[(this._get(inst, 'isRTL') ? 'add' : 'remove') +
 			'Class']('ui-datepicker-rtl');
 		if (inst == $.datepicker._curInst && $.datepicker._datepickerShowing && inst.input &&
-				inst.input.is(':visible') && !inst.input.is(':disabled'))
+				// #6694 - don't focus the input if it's already focused
+				// this breaks the change event in IE
+				inst.input.is(':visible') && !inst.input.is(':disabled') && inst.input[0] != document.activeElement)
 			inst.input.focus();
 		// deffered render of the years select (to avoid flashes on Firefox) 
 		if( inst.yearshtml ){