ffprobe: add -o option

This enables printing to a resource specified with -o OUTPUT.

In case the output is not specified, prints to stdout as usual.

Address issue: http://trac.ffmpeg.org/ticket/8024Signed-off-by: Marton Balint <cus@passwd.hu>

Changelog

@@ -19,6 +19,7 @@ version 5.1:
 - blurdetect filter
 - tiltshelf audio filter
 - QOI image format support
+- ffprobe -o option
 
 
 version 5.0:

doc/ffprobe.texi

@@ -28,6 +28,9 @@ If a url is specified in input, ffprobe will try to open and
 probe the url content. If the url cannot be opened or recognized as
 a multimedia file, a positive exit code is returned.
 
+If no output is specified as output with @option{o} ffprobe will write
+to stdout.
+
 ffprobe may be employed both as a standalone application or in
 combination with a textual filter, which may perform more
 sophisticated processing, e.g. statistical processing or plotting.
@@ -348,6 +351,10 @@ on the specific build.
 @item -i @var{input_url}
 Read @var{input_url}.
 
+@item -o @var{output_url}
+Write output to @var{output_url}. If not specified, the output is sent
+to stdout.
+
 @end table
 @c man end