Huge engine change, replace all std::shared_ptrs

Create a new shared pointer type stdext::shared_object_ptr and stdext::shared_obj
using boost::intrusive_ptr

Advantages:
 * half memory usage
 * faster and lightweight

Disadvantages:
 * using weak_ptr is not supported anymore
 * compiling seems slower

src/framework/ui/uimanager.cpp

@@ -285,7 +285,7 @@ void UIManager::onWidgetDestroy(const UIWidgetPtr& widget)
         g_dispatcher.scheduleEvent([backupList] {
             g_lua.collectGarbage();
             for(const UIWidgetPtr& widget : backupList) {
-                if(widget->getUseCount() != 1)
+                if(widget->ref_count() != 1)
                     g_logger.warning(stdext::format("widget '%s' destroyed but still have %d reference(s) left", widget->getId(), widget->getUseCount()-1));
             }
         }, 1);