[RFC] Convert trace data to CTF

A possible extension to BCC can be to convert trace data coming from maps and write it as [CTF](http://diamon.org/ctf/) data. The CTF format is a compact binary trace format which is used by tools such as LTTng and can allow traces to be viewed in a very nice fashion in [Trace Compass](http://tracecompass.org/). This would allow efficient trace storage for post-mortem analysis. Also, it would allow traces to be viewed graphically. Trace Compass has very interesting features such as flame-charts, and critical flow view, resource view (and [many more](https://wiki.eclipse.org/Trace_Compass/News/NewIn20)).

I have done a quick test which can write CTF traces using [babeltrace](http://diamon.org/babeltrace/) library (2.0.0-pre) Here are the results :

```
[suchakra@moria tracing]$ sudo ./open2ctf.py
trace path: /tmp/tmp26ga140x
^C[suchakra@moria tracing]$ babeltrace /tmp/tmp26ga140x
[00:24:50.796162597] (+?.?????????) 0 do_sys_open: { }, { pid = 909, comm = "iio-sensor-prox", filename = "/dev/iio:device2" }
[00:24:50.796399646] (+0.000237049) 0 do_sys_open: { }, { pid = 909, comm = "iio-sensor-prox", filename = "/dev/iio:device4" }
[00:24:50.801229686] (+0.004830040) 0 do_sys_open: { }, { pid = 1206, comm = "gnome-shell", filename = "/proc/self/stat" }
[00:24:50.801430938] (+0.000201252) 0 do_sys_open: { }, { pid = 1734, comm = "gnome-shell", filename = "/proc/self/stat" }
[00:24:50.807656245] (+0.006225307) 0 do_sys_open: { }, { pid = 18399, comm = "gnome-settings-", filename = "/proc/self/fd" }
..
..
```
Here, we collect trace data from `do_sys_open` and save it in CTF, then open the trace using `babeltrace` (which is a trace reader as well). This trace also works with Trace Compass. As we increase number of relevant trace events collected (`sched_*` etc.), Trace Compass would eventually be able to show something like [this](http://archive.eclipse.org/tracecompass/doc/stable/org.eclipse.tracecompass.doc.user/images/TimeAlignment_sash.png). This in PoC stage for now - the clocks and timings have to be improved. The deltas are ok, but wall clock time is not correct. We'll do a helper function in BCC itself that can help write these traces. Expect a PR soon :) If you have suggestions, leave them here!

Start by reviewing the open2ctf.py proof of concept and its babeltrace output for do_sys_open events. Then examine how BCC collects map and sched_* trace data and how CTF timestamps are represented. Done means a defined BCC helper can write traces that babeltrace and Trace Compass read correctly, including improved clock and wall-time handling.

Written by the indexing model from the issue text.