i915g: shadow compares
Regressed from i915c:
+spec@arb_fragment_program_shadow@tex-shadow1d,Fail
+spec@arb_fragment_program_shadow@tex-shadow2d,Fail
+spec@arb_fragment_program_shadow@tex-shadow2drect,Fail
+spec@arb_fragment_program_shadow@txp-shadow1d,Fail
+spec@arb_fragment_program_shadow@txp-shadow2d,Fail
+spec@arb_fragment_program_shadow@txp-shadow2drect,Fail