perf report: Implement Newt callgraphs

Starts collapsed, allows annotating by pressing 'A' or 'a' on
the symbol, be it the top level one or any of the symbols in the
chains.

It (ab)uses the only tree widget in newt, that is actually a
checkbox tree that we use with just one option ('.'), end result
is usable but we really need to create a custom widget tree so
that we can use the data structures we have (hist_entry rb_tree
+ callchain rb_tree + lists), so that we reduce the memory
footprint by not creating a mirror set of data structures in the
newtCheckboxTree widget.

Thanks to Frédéric Weisbacker for fixing the orphanage problem
in 301fde27, without that we were tripping a newt bug (fix
already sent to newt's maintainer).

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1269291169-29820-1-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>