Added a simple new benchmark, SieveBench(N), which allocates an array of

length N and runs the simple Sieve of Eratosthenes (of finding all the
prime numbers below N), which jumps around the array at various strides
and therefore exercises, among other things, the TLB, and can be effected
by whether we use huge pages or normal pages for storing the array.

To allow running this benchmark without increasing the VM's memory,
main() uses N=100,000. But to really see the effect of huge pages,
try N=200,000,000 (commented out in main()).