Avoid back button problem with Iframes in Firefox

Avoid the back button problem with Iframes in Firefox, which causes the need to double click to return to the previous page when Lazyload-xt has already loaded the iframe.

Author: darius-heavy

src/jquery.lazyloadxt.js

@@ -215,7 +215,10 @@
                         src = $isFunction(srcAttr) ? srcAttr($el) : el.getAttribute(srcAttr);
 
                     if (src) {
-                        el.src = src;
+                        if ( el.tagName === 'IFRAME' )
+                            el.contentWindow.location.replace( src );
+                        else
+                            el.src = src;
                     }
 
                     removeNode = true;