STANDALONE_SIMPQS no longer builds

[hvds]

It was first broken by 8a68d5c, which gave utility.c a dependency on factor.[ch] (which then pulls in everything else), and has acquired several additional dependencies since then.

I've been building successfully with:

  -DSTANDALONE_SIMPQS -DSTANDALONE simpqs.c utility.c \
  rootmod.c isaac.c primality.c gmp_main.c factor.c prime_iterator.c tinyqs.c \
  lucas_seq.c real.c bls75.c ecpp.c ecm.c squfof126.c pbrent63.c random_prime.c \
  -lgmp -lm

I'm not sure whether just to update the comment in simpqs.c to include the above list, or start the work to unpick dependencies from utility.c. I don't want to drop it entirely - it's really useful for testing changes.

[hvds]

In #48 I update the comment to include the full list.