
- Examine behavior near 32-bit limit on 32-bit machines.

- GMP versions of all routines.

- prime_count and nth_prime with very large inputs.

- segment sieve should itself use a segment for its primes.
  Today we'd need sqrt(2^64) max = 140MB.  Segmenting would yield under 1MB.

- factoring (Fermat, Pollard Rho, HOLF, etc.)

- Add test to check maxbits in compiled library vs. Perl

- Fill in the synopsis!

- Li(n)

- Pure perl implementations

- input validation (in XS, or do we need to make Perl wrappers for everything?)
