Merge remote-tracking branch 'remotes/kraxel/tags/pull-vnc-20141028-1' into staging

Merge remote-tracking branch 'remotes/kraxel/tags/pull-vnc-20141028-1' into staging

vnc: return directly if no vnc client connected
vnc: sanitize bits_per_pixel from the client (CVE-2014-7815)

# gpg: Signature made Tue 28 Oct 2014 10:52:31 GMT using RSA key ID D3E87138
# gpg: Good signature from "Gerd Hoffmann (work) <[email protected]>"
# gpg:                 aka "Gerd Hoffmann <[email protected]>"
# gpg:                 aka "Gerd Hoffmann (private) <[email protected]>"

* remotes/kraxel/tags/pull-vnc-20141028-1:
  vnc: return directly if no vnc client connected
  vnc: sanitize bits_per_pixel from the client

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