Doc: Define doc-specific typedef for Windows type 'IDataObject'

Without this, the Clang-parser seems to convert the type to 'int'
on non-Windows platforms.

Fixes: QTBUG-78551
Change-Id: I3d727fed8be46ef1a25c4fdf2b10fa3429d784ff
Reviewed-by: Paul Wicking <paul.wicking@qt.io>