perf tools: Add support to parse event group syntax

Adding scanner/parser bits to parse event groups.

The grammar for group is:
  groups:      groups ',' group | group
  group:       group_name '{' events '}' group_mod
  group_name:  name | empty
  group_mod:   ':' group_mods | empty
  group_mods:  event_mod

It's possible to use standard event modifier as a modifier
for group. It'll be used as an update to existing event
modifiers.

It's necessary to use quoting ("'\) when specifying group on
command line, since {} characters are interpreted by most of
the shells.

It is now possible to specify groups in event syntax like:

  '{cycles,faults}'
   - anonymous group

  'group1{cycles,faults}
   - group with name 'group1'

  '{cycles,faults}:k
   - anonymous group with event modifier 'k'

  '{cpu-clock,task-clock},{minor-faults,major-faults}'
   - two anonymous groups

The grouping functionality itself is coming shortly.

Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ulrich Drepper <drepper@gmail.com>
Link: http://lkml.kernel.org/n/tip-p4j8bnvo879uokum4k4zk5q6@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 3ec4bfc..57d5809 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -611,19 +611,29 @@
 			 pmu_event_name(head_config));
 }
 
+int parse_events__modifier_group(struct list_head *list __used,
+				 char *event_mod __used)
+{
+	return 0;
+}
+
+void parse_events__group(char *name __used, struct list_head *list __used)
+{
+}
+
 void parse_events_update_lists(struct list_head *list_event,
 			       struct list_head *list_all)
 {
 	/*
 	 * Called for single event definition. Update the
-	 * 'all event' list, and reinit the 'signle event'
+	 * 'all event' list, and reinit the 'single event'
 	 * list, for next event definition.
 	 */
 	list_splice_tail(list_event, list_all);
 	free(list_event);
 }
 
-int parse_events_modifier(struct list_head *list, char *str)
+int parse_events__modifier_event(struct list_head *list, char *str)
 {
 	struct perf_evsel *evsel;
 	int exclude = 0, exclude_GH = 0;