Merge remote-tracking branch 'remotes/berrange/tags/pull-qcrypto-2016-09-12-1' into staging

Merge qcrypto 2016/09/12 v1

# gpg: Signature made Mon 12 Sep 2016 12:02:20 BST
# gpg:                using RSA key 0xBE86EBB415104FDF
# gpg: Good signature from "Daniel P. Berrange <dan@berrange.com>"
# gpg:                 aka "Daniel P. Berrange <berrange@redhat.com>"
# Primary key fingerprint: DAF3 A6FD B26B 6291 2D0E  8E3F BE86 EBB4 1510 4FDF

* remotes/berrange/tags/pull-qcrypto-2016-09-12-1:
  crypto: report enum strings instead of values in errors
  crypto: fix building complaint
  crypto: ensure XTS is only used with ciphers with 16 byte blocks

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