tools lib traceevent: Add destructor for format_field

Move the calls that frees the resources allocated for a struct format_field to
a separate routine.

Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1426790181-19118-1-git-send-email-dsahern@gmail.com
[ Split this part from a larger patch, added pevent_ prefix as requested by Steven ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/lib/traceevent/event-parse.h b/tools/lib/traceevent/event-parse.h
index 5b4efc0..6abda54 100644
--- a/tools/lib/traceevent/event-parse.h
+++ b/tools/lib/traceevent/event-parse.h
@@ -619,6 +619,7 @@
 				      const char *buf,
 				      unsigned long size, const char *sys);
 void pevent_free_format(struct event_format *event);
+void pevent_free_format_field(struct format_field *field);
 
 void *pevent_get_field_raw(struct trace_seq *s, struct event_format *event,
 			   const char *name, struct pevent_record *record,