The original code is the Network Security Services (NSS), licensed under
the MPL/GPL/LGPL tri-license (http://www.mozilla.org/MPL/).

We extracted the SHA-256 source files, eliminated unneeded dependencies,
deleted or commented out unused code, and tweaked them for Chrome's source
tree.  sha512.c is renamed sha512.cc so that it can include Chrome's C++
header "base/basictypes.h".  We define NOUNROLL256 to reduce the object code
size.