Both the ARBfp and fixed-function blitter support
WINED3D_BLIT_OP_COLOR_BLIT_ALPHATEST, but the fixed-function blitter requires
a compatibility context, and the ARBfp blitter isn't created when the GLSL
blitter is available.

This fixes a regression introduced by commit
6fc027e5.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=45874Signed-off-by: Henri Verbeet <hverbeet@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>