Merge remote-tracking branch 'remotes/stefanha/tags/tracing-pull-request' into staging

Merge remote-tracking branch 'remotes/stefanha/tags/tracing-pull-request' into staging

# gpg: Signature made Mon 14 Mar 2016 11:27:01 GMT using RSA key ID 81AB73C8
# gpg: Good signature from "Stefan Hajnoczi <[email protected]>"
# gpg:                 aka "Stefan Hajnoczi <[email protected]>"

* remotes/stefanha/tags/tracing-pull-request:
  trace: separate MMIO tracepoints from TB-access tracepoints
  trace: include CPU index in trace_memory_region_*()

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