perf: New migration tool overview

perf: New migration tool overview

This brings a GUI tool that displays an overview of the load
of tasks proportion in each CPUs.

The CPUs forward progress is cut in timeslices. A new timeslice
is created for every runqueue event: a task gets pushed out or
pulled in the runqueue.

For each timeslice, every CPUs rectangle is colored with a red
power that describes the local load against the total load.
This more red is the rectangle, the higher is the given CPU load.
This load is the number of tasks running on the CPU, without
any distinction against the scheduler policy of the tasks, for
now.

Also for each timeslice, the event origin is depicted on the
CPUs that triggered it using a thin colored line on top of the
rectangle timeslice.

These events are:

* sleep: a task went to sleep and has then been pulled out the
  runqueue. The origin color in the thin line is dark blue.

* wake up: a task woke up and has then been pushed in the
  runqueue. The origin color is yellow.

* wake up new: a new task woke up and has then been pushed in the
  runqueue. The origin color is green.

* migrate in: a task migrated in the runqueue due to a load
  balancing operation. The origin color is violet.

* migrate out: reverse of the previous one. Migrate in events
  usually have paired migrate out events in another runqueue.
  The origin color is light blue.

Clicking on a timeslice provides the runqueue event details
and the runqueue state.

The CPU rectangles can be navigated using the usual arrow
controls. Horizontal zooming in/out is possible with the
"+" and "-" buttons.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Venkatesh Pallipadi <venki@google.com>
Cc: Pierre Tardy <tardyp@gmail.com>
Cc: Nikhil Rao <ncrao@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>