[Lazarus] LCLWidgetType CustomDrawn

[Michael Schnell]

As I am myself I obviously need to ask these questions:

  - To me it looks like "CustomDrwan" can't be sure that any back ent it 
is made for provides an event queue. So it supposedly needs to create an 
event queue in the LCL code. Here of course the main thread needs do so 
a non-busy wait for incoming events using the underlying OS API. Correct ?

- As the purpose of CustomDrawn seems to be an interface between the 
normal LCL stuff and the Backend-depending functions that is as simple 
as possible so that new Backends can easily be attached, I suppose it 
would be very viable to create Backends like:
  - "noGUI" (the drawing functions are strictly dummy doing nothing)
  - "ifi" (the backend is attached via a bidirectional byte stream such 
as a pipe, a socket or an asynchronous port.
  - http (the backend is done in java script and runs in a browser, the 
connection is done using the http protocol <see ExtPascal / ExtJS>)

-Michael