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

# gpg: Signature made Tue 01 Mar 2016 15:48:04 GMT using RSA key ID 81AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>"
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>"

* remotes/stefanha/tags/tracing-pull-request:
  trace: Add a proper API to manage auto-generated events from the 'tcg' property
  trace: Add 'vcpu' event property to trace guest vCPU
  typedefs: Add CPUState
  trace: Add helper function to cast event arguments
  tcg: Move definition of type TCGv
  tcg: Add type for vCPU pointers
  trace: Remove unnecessary intermediate event copies
  trace: Extend API to manage event arguments
  vl: fix tracing initialization
  trace: use addresses instead of offsets in memory tracepoints
  trace: split subpage MMIOs into their own trace events.
  trace: docs: "simple" backend does support strings
  trace: drop trailing empty strings

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