perf trace: Implement -o/--output filename

To output all 'trace' output to a filename, just like 'strace -ofile'

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-6q1homkwoayhmoq64y5vhel6@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf-trace.txt

@@ -30,6 +30,10 @@ OPTIONS
 --expr::
 	List of events to show, currently only syscall names.
 
+-o::
+--output=::
+	Output file name.
+
 -p::
 --pid=::
 	Record events on existing process ID (comma separated list).