Update demo.
Check EVP errors for handshake digests.

Partial mitigation of PR#3200
(cherry picked from commit 0294b2be5f4c11e60620c0018674ff0e17b14238)
PPC assembly pack: improve AIX support (enable vpaes-ppc).
sha512.c: fullfull implicit API contract in SHA512_Transform.

SHA512_Transform was initially added rather as tribute to tradition
than for practucal reasons. But use was recently found in ssl/s3_cbc.c
and it turned to be problematic on platforms that don't tolerate
misasligned references to memory and lack assembly subroutine.
PPC assembly pack update addendum.
evp/e_[aes|camellia].c: fix typo in CBC subroutine.

It worked because it was never called.
sha1-x86_64.pl: harmonize Win64 SE handlers for SIMD code pathes.
(and ensure stack alignment in the process)