This limit is fixed in Mesa core and cannot be changed.
It only affects ARB_vertex_program and ARB_fragment_program.

The minimum value for ARB_vertex_program is 1 according to the spec.
The maximum value for ARB_vertex_program is limited to 1 by Mesa core.

The value should be zero for ARB_fragment_program, because it doesn't
support ARL.

Finally, drivers shouldn't mess with these values arbitrarily.

Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>