check that the index returned is a minimum, rather than the exact value from numpy (in case of duplicate min/maxs)

aliasing (closes inducer/loopy#69).

read-only.

This restriction previously applied to global temporaries.

unscheduled instructions (closes #9).

The check is to make sure that a non-global temporary gets a
definition within every subkernel that uses it.

Also make lp.save_and_reload_temporaries.