As preparation for the next patch. Note that we drop WINED3DUSAGE_RENDERTARGET
here. We never render directly to the back-buffer in ddraw, since ddraw
back-buffers don't directly correspond to wined3d back-buffers. Moreover,
ddraw may create WINED3DFMT_P8_UINT swapchains, for which
WINED3DUSAGE_RENDERTARGET wouldn't be valid.
Signed-off-by: Henri Verbeet <hverbeet@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>