[31599] Deprecated JSubMenuHelper in mod_submenu

Small correction in the submenu module that is using a deprecated class.

2013-07-28T22:11:05+00:00	WARNING	deprecated	JSubMenuHelper::getEntries() is deprecated. Use JHtmlSidebar::getEntries() instead.
2013-07-28T22:11:05+00:00	WARNING	deprecated	JSubMenuHelper::getFilters() is deprecated. Use JHtmlSidebar::getFilters() instead.
2013-07-28T22:11:05+00:00	WARNING	deprecated	JSubMenuHelper::getAction() is deprecated. Use JHtmlSidebar::getAction() instead.