TreeView notifications fix

[Mike Hearn]

Thanks! Where did you find this list, for future reference? :)

Oh, and I don't suppose you know where in Wine they are registered (with
RegisterClass) do you? Or are they so special they don't need
registering....

> Indeed, here is a list of system classes:
> 
> Class      Description 
> ---------- --------------------------------------------------------------
> ComboLBox  The class for the list box contained in a combo box. 
> DDEMLEvent Windows NT/Windows 2000/Windows XP: The class for Dynamic Data
>            Exchange Management Library (DDEML) events. 
> Message    Windows 2000/Windows XP: The class for a message-only window. 
> #32768     The class for a menu. 
> #32769     The class for the desktop window. 
> #32770     The class for a dialog box. 
> #32771     The class for the task switch window. 
> #32772     Windows NT/Windows 2000/Windows XP: The class for icon titles.