Merge remote-tracking branch 'remotes/elmarco/tags/ivshmem-fix-pull-request' into...

# gpg: Signature made Wed 13 Apr 2016 11:04:51 BST using RSA key ID 75969CE5
# gpg: Good signature from "Marc-André Lureau <[email protected]>"
# gpg:                 aka "Marc-André Lureau <[email protected]>"
# gpg: WARNING: This key is not certified with sufficiently trusted signatures!
# gpg:          It is not certain that the signature belongs to the owner.
# Primary key fingerprint: 87A9 BD93 3F87 C606 D276  F62D DAE8 E109 7596 9CE5

* remotes/elmarco/tags/ivshmem-fix-pull-request:
  ivshmem: fix ivshmem-{plain,doorbell} crash without arg

Signed-off-by: Peter Maydell <[email protected]>