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 Thu 31 Mar 2016 13:35:23 BST 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-events: Fix typos (found by codespell)
  log: move qemu_log_close/qemu_log_flush from header to log.c
  trace: do not always call exit() in trace_enable_events
  docs: Update documentation for stderr (now log) tracing backend.

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