math/pgen.c: Have `steps' and `tests' count down as documented.
This was how they worked originally, but they were changed a long time
ago to count up from zero instead. This makes it impossible for a
stepper or tester function to know in advance how many times it will be
invoked, which turns out to be important for a forthcoming change.
The reason it was changed wasn't explained in the commit
(
283b9af095a5b24ae71b49a6d2dcbdcdaae47c40) that made it, but I deduce
that it was so that `pgen_test' could identify the first test round and
use the somewhat faster approach of using (the residue whose Montgomery
REDC representative is) 2, rather than a random witness. That change
has now been undone, so we can restore the documented behaviour.
~mdw / catacomb / commit