Merge remote-tracking branch 'remotes/kraxel/tags/ui-20180216-pull-request' into...

bugfixes for vnc and sdl2

# gpg: Signature made Fri 16 Feb 2018 11:53:37 GMT
# gpg:                using RSA key 4CB6D8EED3E87138
# gpg: Good signature from "Gerd Hoffmann (work) <kraxel@redhat.com>"
# gpg:                 aka "Gerd Hoffmann <gerd@kraxel.org>"
# gpg:                 aka "Gerd Hoffmann (private) <kraxel@gmail.com>"
# Primary key fingerprint: A032 8CFF B93A 17A7 9901  FE7D 4CB6 D8EE D3E8 7138

* remotes/kraxel/tags/ui-20180216-pull-request:
  ui: extend VNC trottling tracing to SASL codepaths
  ui: check VNC audio frequency limit at time of reading from client
  ui: avoid 'local_err' variable shadowing in VNC SASL auth
  ui: avoid risk of 32-bit int overflow in VNC buffer check
  sdl2: fix mouse grab
  sdl: restore optimized redraw
  vnc: fix segfault in closed connection handling
  vnc: add qapi/error.h include to stubs
  vnc: remove bogus object_unref on client socket

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