Instances where direction was determined based on
winsys or user fbo and should be determined based on
FlipY.

Key STATE_FB_WPOS_Y_TRANSFORM for of FlipY instead of
_mesa_is_user_fbo.  This corrects gl_FragCoord usage
when applying GL_MESA_framebuffer_flip_y.

Fixes: ab05dd18

 ("i965: implement GL_MESA_framebuffer_flip_y [v3]")
Reviewed-by: Brian Paul <brianp@vmware.com>