For Java drag source, choosing an action other than the user action shows a no-drop cursor

This bug affects a recent Swing DnD enhancement. Please fix it ASAP.

- Please compile and run the attached demo.
(NOTE: Requires Swing's b74 integration to run the attached test,
 but problem is unrelated to Swing changes)

- On the left is a JList drag source with supported actions COPY and MOVE.
- On the right are two JLists that both accept drops.
- The top one chooses the MOVE action (through Swing with acceptDrag(MOVE))
- The bottom one chooses the COPY action (through Swing with acceptDrag(COPY))
- Drag from the source into the top list and it works
- Drag from the source into the bottom list and it shows the NO-DROP cursor
  It still allows drops. But the wrong cursor is shown.
- Drag text from a native text editor (that supports COPY and MOVE) and
  you'll see that the same problem doesn't exist.

The problem is that Java is showing the NO-DROP drop cursor when you choose something other than the user drop action.
This is wrong - you should be able to choose any of the supported source actions, like with a native drag source.

I suspect the problem is the method DragSourceDragEvent.getDropAction(). Right now it does:

return dropAction & targetActions & getDragSourceContext().getSourceActions();

This is wrong, since it shouldn't intersect the user drop action (dropAction).

Changing it to the following fixes the problem:

return targetActions & getDragSourceContext().getSourceActions(); // note that targetActions is really just the single chosen target action

-----------------------------

The problem can also be reproduced in another way on Windows XP:

- Launch SwingSet2.
- Launch Microsoft's WordPad
- Select "Enable Dragging" in the options menu
- In the internal frames demo, select text and drag from the text field labeled "Frame title"
- Drag into WordPad.
- WordPad always selects the COPY option. Notice that this causes the NO_DROP cursor.
- HOWEVER, even though the wrong cursor is shown, you can still drop.