Qt: remember last opened directory

(cherry picked from commit 547a75774fd99b5c3a1223b1e2361f78f821d9b9)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/gui/qt4/dialogs_provider.cpp

@@ -506,6 +506,8 @@ static void openDirectory( intf_thread_t *p_intf, bool pl, bool go )
     if( dir.isEmpty() )
         return;
 
+    p_intf->p_sys->filepath = qtu( dir );
+
     const char *scheme = "directory";
     if( dir.endsWith( "/VIDEO_TS", Qt::CaseInsensitive ) )
         scheme = "dvd";