wined3d: Use "depth_size"/"stencil_size" to check for depth/stencil formats in arbfp_blit_supported().

The idea is to get rid of the WINED3DFMT_FLAG_DEPTH and
WINED3DFMT_FLAG_STENCIL format flags, and instead introduce a flag similar to
WINED3DFMT_FLAG_RENDERTARGET that indicates whether the format can be used
with WINED3D_BIND_DEPTH_STENCIL.
Signed-off-by: Henri Verbeet <hverbeet@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>