Add Profiler object and fields.
Add profiler extension API. It notifies Profiler objects with
real-time performance data.
Add module that implements the profiler extension.
Add pw-profiler tool that binds to the profiler API and dumps the
data into a log file, gnuplot files, a html page and a script to
generate svg graphs. This is almost the same as what JACK2
JackEngineProfiling does.
