Comment 2 for bug 1219052

Thanks for the portable endian.h retrofit: there are likely lots
of additional issues just fixed in the NIST SHA3 digests that just got
fixed as well.

There's a number of tricky non-portable GNUisms in set.c, including " … "
initialization as well as the remaining nested static function in need of fixing.

See the -DSELF_TEST which absolutely MUST pass for any serious refactoring
of the rpmio/set.c code: the algorithm is quite complex, debugging any serious
breakage would take a week or more to figure out.