draw3: don't Destroy widgets that have a parent set

+ parent should destroy the widgets
+ left calling Destroy on widgets that set their parent to NULL (setting / not setting the parent doesn't seem to follow any rule)
+ Destroy'ing led to segfault on wxUninitialize (wxAppBase::CleanUp)

wx/draw3/drawpnl.cpp

@@ -529,20 +529,10 @@ DrawPanel::~DrawPanel()
 #ifdef WXAUI_IN_PANEL
 	am.UnInit();
 #endif
-
-	if (dinc != NULL)
-		dinc->Destroy();
-	if (sinc != NULL)
-		sinc->Destroy();
-	if (dtd != NULL)
-		dtd->Destroy();
-	if (ee != NULL)
-		ee->Destroy();
 	if (dbtw != NULL)
 		dbtw->Destroy();
 	smw->Destroy();
 	rw->Destroy();
-	pw->Destroy();
 
 	delete dw;