[D3D8] fix compile error for missing GL define

[H. Verbeet]

On 18/01/06, Robert Reif <reif at earthlink.net> wrote:
> I don't know the best way to handle this but this patch does get it to
> compile again.
Fixing it that way makes it a compile time check instead of a runtime
check. I think the idea was for d3d to check extension support during
runtime.

include/wine/wined3d_gl.h has defines for GL_ARB_point_sprite etc, but
as far as I know it doesn get included by d3d8. For d3d8, it should
probably be defined in dlls/d3d8/d3dcore_gl.h (it isn't right now).