glsl: Mark program as using dFdy if coarse/fine variant is used

Signed-off-by: Chris Forbes <chrisf@ijw.co.nz>
Reviewed-by: Matt Turner <mattst88@gmail.com>
i965/vec4: Assert that fine/coarse derivative ops don't appear

Signed-off-by: Chris Forbes <chrisf@ijw.co.nz>
Reviewed-by: Matt Turner <mattst88@gmail.com>
i965/fs: Support fine/coarse derivative opcodes

The quality level (fine/coarse/dont-care) is plumbed through to the
generator as a constant in src1.

Signed-off-by: Chris Forbes <chrisf@ijw.co.nz>
Reviewed-by: Matt Turner <mattst88@gmail.com>
i965: Enable ARB_derivative_control on Gen7+.

The extension says GL 4.0 is required. We'll meet the spirit
of that restriction by enabling on just those generations which will
soon support GL 4.0 (Gen7+), although it's technically supportable on
all generations.

Signed-off-by: Chris Forbes <chrisf@ijw.co.nz>
Reviewed-by: Matt Turner <mattst88@gmail.com>
docs: Mark off ARB_derivative_control for i965.

Also update 10.3 relnotes to match.

Signed-off-by: Chris Forbes <chrisf@ijw.co.nz>
Reviewed-by: Matt Turner <mattst88@gmail.com>