i965: fix polygon face orientation when rendering to FBO

i965: fix polygon face orientation when rendering to FBO

In the i965, the FBO coordinate system is inverted from the standard
OpenGL/Mesa coordinate system; that means that the viewport and the
polygon face orientation have to be inverted if rendering to a FBO.

The viewport was already being handled correctly; but polygon face
was not.  This caused a conform failure when rendering to texture with
two-sided lighting enabled.

This fixes the problem in the i965 driver, and adds to the comment about
the gl_framebuffer "Name" field so that this isn't a surprise to other
driver writers.