Fix building under Linux

stupid linux
Add rudimentary (unrelated to base64) speed test

Example output (OS X):
matt@ununoctium:~/repos/crc64-compare% ./crc64-redis 20 10000
Average call overhead: 0.050300 microseconds
Wrote 200000 MB in 8.419044 seconds for a speed of 23755.667969 MB/s (23.198895 GB/s)

So far it doesn't work at all under Linx because Linux is optimizing the
memsets away into taking almost zero time, no matter how much we set.
Free something before we exit

Because we're nice programmers
Break out mem-speed into its own executable

Also, now it works under Linux and OS X.  That's called progress.
Add nicer wording and add modern bogos

Meaningless, but at least it's more numbers.
Add note about mem-speed