This borrows heavily from the Mesa project's perfetto instrumentation, and
for now just adds perfetto to the build and a collection of useful macros
for adding trace points.
The atomics have been cargo culted in - Weston currently has no need of
such things, but I guess they're harmless for now and could be useful if
we consider threads in the future.
Signed-off-by: Derek Foreman <derek.foreman@collabora.com>
