让firefox支持innerText属性

<!--
//
 // patch of innerText for firefox
 //
(function (bool) {
     function setInnerText(o, s) {
         while (o.childNodes.length != 0) {
             o.removeChild(o.childNodes[0]);
         }

         o.appendChild(document.createTextNode(s));
     }

     function getInnerText(o) {
         var sRet = "";

         for (var i = 0; i < o.childNodes.length; i ++) {
             if (o.childNodes[i].childNodes.length != 0) {
                 sRet += getInnerText(o.childNodes[i]);
             }

             if (o.childNodes[i].nodeValue) {
                 if (o.currentStyle.display == "block") {
                     sRet += o.childNodes[i].nodeValue + "\n";
                 } else {
                     sRet += o.childNodes[i].nodeValue;
                 }
             }
         }

         return sRet;
     }

     if (bool) {
         HTMLElement.prototype.__defineGetter__("currentStyle", function () {
             return this.ownerDocument.defaultView.getComputedStyle(this, null);
         });

         HTMLElement.prototype.__defineGetter__("innerText", function () {
             return getInnerText(this);
         })

         HTMLElement.prototype.__defineSetter__("innerText", function(s) {
             setInnerText(this, s);
         })
     }
 })(/Firefox/.test(window.navigator.userAgent));
//-->