Optimize and preload message icons

skins/larry/templates/login.html

@@ -39,11 +39,13 @@
 
 <roundcube:object name="preloader" images="
   /images/ajaxloader.gif
+  /images/ajaxloader_dark.gif
   /images/buttons.png
   /images/addcontact.png
   /images/filetypes.png
   /images/listicons.png
   /images/messages.png
+  /images/messages_dark.png
   /images/quota.png
   /images/selector.png
   /images/splitter.png