base/primes.jl: faster primes(n) and isprime(n) functions.

Sieve of Atkin for generating primes:

	http://en.wikipedia.org/wiki/Sieve_of_Atkin

Code very loosely based on this:

	http://thomasinterestingblog.wordpress.com/2011/11/30/generating-primes-with-the-sieve-of-atkin-in-c/
	http://dl.dropboxusercontent.com/u/29023244/atkin.cpp

Miller-Rabin for primality testing:

	http://en.wikipedia.org/wiki/Miller–Rabin_primality_test
isprime(n): better witness choices for various n.

http://mathoverflow.net/questions/101922/smallest-collection-of-bases-for-prime-testing-of-64-bit-numbers
http://primes.utm.edu/prove/merged.html
http://miller-rabin.appspot.com