user32/tests: add tests that shows problems how Wine ends menu tracking in the WM_CANCELMODE message handling.

[Rein Klazes]

Hi,

Next bug mentioned in bug#9615: drop down menu's do not close followed by
crashes.

Here are tests that show the following problem with the handling of 
WM_CANCELMODE
in the default window procedure, causing menu's that do no close or close
prematurely:

1. menu's owned by child windows
2. menu's can be closed from top level windows that do not have a 
relationship
  with the open menu
3. menu's do proceed if  they are still initializing.

A possible fix for the frst 2 problems will follow soon.

Rein.