C99 translation of Geoff Pike's and Jyrki Alakuijala's FarmHash.
This version of FarmHash is translated from the code available via github (1.1). For quality and performance metrics, please see Reini Urban's smhasher fork.
The code is meant to be platform agnostic, excluding some compiler intrinsics.
Note, byte swap and rotate right are used. I've confirmed the included
versions optimize correctly with x86 and Clang (3.7), however there may be
platforms or compilers they don't optimize correctly on.