debug-info filter plugin

debug-info filter plugin

This plugin can be inserted in the graph to add the debugging
informations to events that have the necessary context informations (see
the README for usage informations).

Compared to the previous implementation, this version does not only
output the debug informations to the text output, but it adds the
debug_info structure into the CTF events. That way, the plugins and
sinks after this one see the debug_info as part of the event contexts.

The default name of the structure added to the events is "debug_info",
but can be overridden. If this structure already exists in the event
context, it is not added again.

If a trace does not have the ip and vpid event contexts in its stream
class, the trace is copied without adding the "debug_info" structure.

Signed-off-by: Julien Desfossez <jdesfossez@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>