Pixel shader 1.x constants must be between -1 and 1, or they will be clamped,
even constants defined in the shader.
Also mark 1.x-specific features if any.
This is simply unnecessary and wastes time.
As part of this, simply remove the "all" directive. Only for a couple of tests
is it even potentially interesting to validate all pixels (e.g.
nointerpolation.shader_test), and for those "all" is replaced with an explicit
(0, 0, 640, 480) rect.
In all other cases we just probe (0, 0).
