[user32_apitest]

[user32_apitest]
- In TrackMouseEvent tests, use mouse_event function to move the mouse cause this causes low level hooks to be called and SetCursorPos doesn't
- Test low level mouse hooks for TrackMouseEvent
- Test ways to block WM_MOUSEHOVER and WM_MOUSELEAVE. This is useful to detect where each message is generated
- clean up the code a bit by adding FLUSH_MESSAGES macro that checks for expected message queue status and flushes the message queue

svn path=/trunk/; revision=53855