Small toom52 cleanup

[Niels Möller]

nisse at lysator.liu.se (Niels Möller) writes:

> I've adapted toom43_mul to use a proper itch/scratch interface. I also
> simplified the allocation by requiring that s + t >= 5, so that 5
> temporary values of n+1 limbs each fit in the product area.

I've now checked in analogous changes to toom52, and a new test
program.

an >= 32 is a sufficient condition to ensure that s+t >= 5, and this
is used by the test prrogram. (A previous comment stated that n > 6 is
sufficient, but a counter example with n = 7 is an = 31, bn = 8, which
gives s = 3, t = 1).

Regards,
/Niels