Merge remote-tracking branch 'remotes/rth/tags/pull-tcg-20170426' into staging

Merge remote-tracking branch 'remotes/rth/tags/pull-tcg-20170426' into staging

Fix for exit_atomic tcg opcode paths

# gpg: Signature made Wed 26 Apr 2017 18:27:11 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-tcg-20170426:
  tcg: Initialize return value after exit_atomic

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