Merge remote-tracking branch 'remotes/rth/tags/pull-s390-20170717' into staging

Queued s390x tcg patches, v2

# gpg: Signature made Mon 17 Jul 2017 22:22:23 BST
# gpg:                using RSA key 0xAD1270CC4DD0279B
# gpg: Good signature from "Richard Henderson <rth7680@gmail.com>"
# gpg:                 aka "Richard Henderson <rth@redhat.com>"
# gpg:                 aka "Richard Henderson <rth@twiddle.net>"
# Primary key fingerprint: 9CB1 8DDA F8E8 49AD 2AFC  16A4 AD12 70CC 4DD0 279B

* remotes/rth/tags/pull-s390-20170717:
  target/s390x: Fix risbg handling
  target/s390x: Allow to enable "idtes" feature for TCG
  target/s390x: Mark ETF3 and ETF3_ENH facilities as available
  target/s390x: Implement TRTR
  target/s390x: Implement SRSTU
  target/s390x: Tidy SRST
  target/s390x: Implement CONVERT UNICODE insns
  target/s390x: Implement CSST

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