Use a form for the Try Again button in error pages

Fixes: https://bugs.launchpad.net/midori/+bug/784931

data/error.html

@@ -68,10 +68,12 @@ description {
             <h1>{title}</h1>
             <p id="message">{message}</p>
             <p id="description">{description}</p>
-            <button onclick="location.reload()">
+            <form method="GET" action="{uri}">
+                <button type="submit" onclick="location.reload(); return false;">
                     <img src="{stock}/gtk-refresh"/>
                     <span>{tryagain}</span>
                 </button>
+            </form>
         </div>
         <br style="clear: both;"/>
     </div>

midori/midori-view.c

@@ -1479,6 +1479,7 @@ midori_view_display_error (MidoriView*     view,
             "{tryagain}", try_again,
             "{res}", res_root,
             "{stock}", stock_root,
+            "{uri}", uri,
             NULL);
         g_free (title_escaped);
         g_free (template);