Bugs in drag and drop

[Wim Oudshoorn]

While implementing drag and drop I noticed a few glitches and bugs

* drag enter is only called after a mouse move
* drag exit is not always called
* the mouse cursor does not indicate correctly 
        what kind of action is associated 
        with the drag and drop.
* during drag and drop you can not switch the action
        with the modifier keys.

At the moment I am halfway fixing these problems.  
THe first two I have fixed. But this will be 
quite a big patch because at the same time 
I reorganized the code quite substentially.

I am not sure if this is acceptable, so
before continuing this way I would like to know
that there is a reasonable chance that 
such a patch will be incorperated.
The patch will not be orthogonal 
to the patch that I send a few
days ago on the crash during dragging.


If there are questions/doubts on the patch
I provided I will be happy to clarify/change the patch.


Wim Oudshoorn.

P.S.:  I do not really expect my patches to be
accepted as is, and carefully reviewing patches 
is very good.