Cause of bug discovered by Jason Edmeades.

Some applications partially overlap the two buffers, so don't assume they
don't overlap.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=38558Signed-off-by: Gabriel Ivăncescu <gabrielopcode@gmail.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>