Datepicker: Properly handle datepickers attached to inputs that are h…

…idden using CSS. Fixes #6988 - Datepicker: Treat all hidden text fields the same.

(cherry picked from commit 6fbee255d8d895c7e84a4b2eaad2cfadc8a3425a)

ui/jquery.ui.datepicker.js

@@ -754,7 +754,7 @@ $.extend(Datepicker.prototype, {
 	_findPos: function(obj) {
 		var inst = this._getInst(obj);
 		var isRTL = this._get(inst, 'isRTL');
-        while (obj && (obj.type == 'hidden' || obj.nodeType != 1)) {
+        while (obj && (obj.type == 'hidden' || obj.nodeType != 1 || $.expr.filters.hidden(obj))) {
             obj = obj[isRTL ? 'previousSibling' : 'nextSibling'];
         }
         var position = $(obj).offset();