perf report: Allow limiting the number of entries to print in callchains

Works by adding a third parameter to the '-g' argument, after the graph
type and minimum percentage, for example:

[root@doppio linux-2.6-tip]# perf report -g fractal,0.5,2

Will show only the first two symbols where at least 0.5% of the samples
took place.

All the other symbols that don't fall outside these constraints will be
put together in the last entry, prefixed with "[...]" and the total
percentage for them.

Suggested-by: Arjan van de Ven <arjan@linux.intel.com>
Acked-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/callchain.h b/tools/perf/util/callchain.h
index 0f4da09..1cba1f5 100644
--- a/tools/perf/util/callchain.h
+++ b/tools/perf/util/callchain.h
@@ -34,6 +34,7 @@
 
 struct callchain_param {
 	enum chain_mode 	mode;
+	u32			print_limit;
 	double			min_percent;
 	sort_chain_func_t	sort;
 };