This commit adds `cargo update` to the distclean target in the
makefile. This updates the Cargo.lock file when clearing the
deps directory.
In addition, it adds a faster implementation of the Sieve of
Eratosthenes for use by `src/factor/gen_table.rs` and `test/factor.rs`.
This change does the following:
1. Updates the arithmetic functions in `src/factor/numeric.rs` to
correctly handle all cases up to 2^64. When numbers are larger
than 2^63, we fall back to slightly slower routines that check
for and handle overflow.
2. Since the arithmetic functions will now not overflow, we no longer
need the safety net trial division implementation. We now always
use Pollard's rho after eliminating small (<=13 bit) primes.
3. Slight tweak in `src/factor/gen_table.rs` to generate the first
1027 primes, which means we test every prime of 13 or fewer bits
before going into Pollard's rho. Includes corresponding update in
`src/factor/prime_table.rs` and the Makefile to reflect this.
4. Add a new test that generates random numbers with exclusively
large (14 to 50 bit) prime factors. This exercises the possible
overflow paths.
5. Add another new test that checks the `is_prime()` function against
a few dozen 64-bit primes. Again this is to exercise possible
overflow paths.
Add a test for `factor`.
This commit also pulls factor's Sieve implementation into its own module
so that the factor test can use it.
Finally, slight refactoring for clarity in gen_table.rs.
