Merge remote-tracking branch 'remotes/berrange-gitlab/tags/crypto-and-more-pull-request' into staging

Merge crypto updates and misc fixes

 * Introduce a GNUTLS backend for crypto algorithms
 * Change crypto library preference gnutls > gcrypt > nettle > built-in
 * Remove built-in DES impl
 * Remove XTS mode from built-in AES impl
 * Fix seccomp rules to allow resource info getters
 * Fix migration performance test
 * Use GDateTime in io/ and net/rocker/ code
 * Improve docs for -smp

# gpg: Signature made Wed 14 Jul 2021 15:08:00 BST
# gpg:                using RSA key DAF3A6FDB26B62912D0E8E3FBE86EBB415104FDF
# gpg: Good signature from "Daniel P. Berrange <dan@berrange.com>" [full]
# gpg:                 aka "Daniel P. Berrange <berrange@redhat.com>" [full]
# Primary key fingerprint: DAF3 A6FD B26B 6291 2D0E  8E3F BE86 EBB4 1510 4FDF

* remotes/berrange-gitlab/tags/crypto-and-more-pull-request: (26 commits)
  qemu-options: rewrite help for -smp options
  qemu-options: tweak to show that CPU count is optional
  qemu-options: re-arrange CPU topology options
  docs: fix typo s/Intel/AMD/ in CPU model notes
  tests/migration: fix unix socket migration
  seccomp: don't block getters for resource control syscalls
  io: use GDateTime for formatting timestamp for websock headers
  net/rocker: use GDateTime for formatting timestamp in debug messages
  crypto: prefer gnutls as the crypto backend if new enough
  crypto: add gnutls pbkdf provider
  crypto: add gnutls hmac provider
  crypto: add gnutls hash provider
  crypto: add gnutls cipher provider
  crypto: introduce build system for gnutls crypto backend
  crypto: flip priority of backends to prefer gcrypt
  crypto: replace 'des-rfb' cipher with 'des'
  crypto: delete built-in XTS cipher mode support
  crypto: delete built-in DES implementation
  crypto: add crypto tests for single block DES-ECB and DES-CBC
  crypto: drop custom XTS support in gcrypt driver
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>