Appart from the by-design type-punned use in CreateWindowEx, m_uID is (only)
used in a call to MAKEWPARAM (to create a WPARAM to pass into a SendMessage
call), so the most realistic type to use seems to be WORD.  And
CHatchWindow::Init is only called with a value of 2000 (from docholder.cxx),
anyway.

Change-Id: I4b6554d1ca9bb3926378c9e25a5473609f5951c5