Changes made since 1.0.1 (2019/06/30).

Implemented a little-known SHA-2 Maj() optimization proposed by Wei Dai.


	Changes made between 1.0.0 (2018/07/12) and 1.0.1 (2019/06/30).

Fill the destination buffer with all set bits on error for fail-safety
of the caller's "< target" check in case the caller neglects to check
for errors.

Simplified SMix2 for its final invocation with Nloop=2 in yespower 0.5.

Revised the "XOR of yespower" tests to trigger duplicate index in the
last SMix2 invocation in yespower 0.5 for N=2048 with at least one of
the values of r being tested.  This is needed to test that a proper
kind of BlockMix is used in that special case, which would previously be
left untested.

Added x32 ABI support (x86-64 with 32-bit pointers).

Added a bit more detail to the README on caching of the computed PoW
hashes when integrating yespower in an altcoin based on Bitcoin Core.