Merge remote-tracking branch 'remotes/agraf/tags/signed-s390-for-upstream' into staging

Patch queue for s390 - 2015-05-13

A few TCG fixes for the s390x target. Nothing special, but with these
applied I can run most of the SLE12 binaries in Linux-user emulation.

# gpg: Signature made Wed May 13 13:49:25 2015 BST using RSA key ID 03FEDC60
# gpg: Good signature from "Alexander Graf <agraf@suse.de>"
# gpg:                 aka "Alexander Graf <alex@csgraf.de>"

* remotes/agraf/tags/signed-s390-for-upstream:
  s390x: Add interlocked access facility 1 instructions
  s390x: Add some documentation in opcode list
  s390x: Fix stoc direction

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