For n larger than 16 we store 16 bytes on each end of the buffer,
eventually overlapping, and then 16 additional bytes for n > 32.

Then we can find a 32-byte aligned range overlapping the remaining part
of the destination buffer, which is filled 32 bytes at a time in a loop.
Signed-off-by: Rémi Bernon <rbernon@codeweavers.com>
Signed-off-by: Piotr Caban <piotr@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>