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

Pull request

Compilation fixes and cleanups for QEMU 4.0.0.

# gpg: Signature made Mon 25 Mar 2019 15:58:28 GMT
# gpg:                using RSA key 9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>" [full]
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>" [full]
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha/tags/tracing-pull-request:
  trace-events: Fix attribution of trace points to source
  trace-events: Delete unused trace points
  scripts/cleanup-trace-events: Update for current practice
  trace-events: Shorten file names in comments
  trace-events: Consistently point to docs/devel/tracing.txt
  trace: avoid SystemTap dtrace(1) warnings on empty files
  trace: handle tracefs path truncation

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