lcl: fix ListBox onChange call on win32 (mantis #0020324)
  - notify TWS class about drag start
  - set csLButtonDown before BeginAutoDrag (there is no dependency in LCL for csLButtonDown in BeginAutoDrag so I see no reason to postpone it)
win32:
  - send TWM_LButtonUp to windows for ListBox if drag operation is started by mouse down

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@42627 4005530d-fff6-0310-9dd1-cebe43e6787f