The buffer size was previously limited to 20 in:

  8d052561

Testing shows that it is somewhere around 1024 on Windows, and using a
smaller buffer causes some input data to be lost with high polling rate
mouses. It can be spotted in Wolfenstein II: New Colossus menus.
Signed-off-by: Rémi Bernon <rbernon@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>