i965: fix polygon stipple when rendering to FBO

i965: fix polygon stipple when rendering to FBO

The polygon stipple pattern, like the viewport and the
polygon face orientation, must be inverted on the i965
when rendering to a FBO (which itself has an inverted pixel
coordinate system compared to raw Mesa).

In addition, the polygon stipple offset, which orients
the stipple to the window system, disappears when rendering
to an FBO (because the window system offset doesn't apply,
and there's no associated FBO offset).

With these fixes, the conform triangle and polygon stipple
tests pass when rendering to texture.