perf_counter tools: Document '--' option parsing terminator

Signed-off-by: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Documentation/perf_counter/Documentation/perf-record.txt

@@ -9,6 +9,7 @@ SYNOPSIS
 --------
 [verse]
 'perf record' [-e <EVENT> | --event=EVENT] [-l] [-a] <command>
+'perf record' [-e <EVENT> | --event=EVENT] [-l] [-a] -- <command> [<options>]
 
 DESCRIPTION
 -----------

Documentation/perf_counter/Documentation/perf-stat.txt

@@ -9,6 +9,7 @@ SYNOPSIS
 --------
 [verse]
 'perf stat' [-e <EVENT> | --event=EVENT] [-l] [-a] <command>
+'perf stat' [-e <EVENT> | --event=EVENT] [-l] [-a] -- <command> [<options>]
 
 DESCRIPTION
 -----------

Documentation/perf_counter/builtin-record.c

@@ -397,7 +397,8 @@ static int __cmd_record(int argc, const char **argv)
 }
 
 static const char * const record_usage[] = {
-	"perf record [<options>] <command>",
+	"perf record [<options>] [<command>]",
+	"perf record [<options>] -- <command> [<options>]",
 	NULL
 };
 

Documentation/perf_counter/builtin-stat.c

@@ -212,6 +212,7 @@ static void skip_signal(int signo)
 
 static const char * const stat_usage[] = {
 	"perf stat [<options>] <command>",
+	"perf stat [<options>] -- <command> [<options>]",
 	NULL
 };