timecode: move timecode muxer options to metadata.

Some demuxers set a timecode in the format or streams metadata. The
muxers now make use of this metadata instead of a duplicated private
option.

This makes possible transparent copy of the timecode when transmuxing
and transcoding.

-timecode option for MPEG1/2 codec is also renamed to -gop_timecode. The
global ffmpeg -timecode option will set it anyway so no option change
visible for the user.

ffmpeg.c

@@ -5618,6 +5618,16 @@ static int opt_deinterlace(const char *opt, const char *arg)
     return 0;
 }
 
+static int opt_timecode(OptionsContext *o, const char *opt, const char *arg)
+{
+    char *tcr = av_asprintf("timecode=%s", arg);
+    int ret = parse_option(o, "metadata:g", tcr, options);
+    if (ret >= 0)
+        ret = opt_default("gop_timecode", arg);
+    av_free(tcr);
+    return ret;
+}
+
 static void parse_cpuflags(int argc, char **argv, const OptionDef *options)
 {
     int idx = locate_option(argc, argv, options, "cpuflags");
@@ -5752,6 +5762,7 @@ static const OptionDef options[] = {
     { "sameq", OPT_BOOL | OPT_VIDEO, {(void*)&same_quant}, "use same quantizer as source (implies VBR)" },
     { "same_quant", OPT_BOOL | OPT_VIDEO, {(void*)&same_quant},
       "use same quantizer as source (implies VBR)" },
+    { "timecode", HAS_ARG | OPT_VIDEO | OPT_FUNC2, {(void*)opt_timecode}, "set initial TimeCode value.", "hh:mm:ss[:;.]ff" },
     { "pass", HAS_ARG | OPT_VIDEO, {(void*)opt_pass}, "select the pass number (1 or 2)", "n" },
     { "passlogfile", HAS_ARG | OPT_VIDEO, {(void*)&opt_passlogfile}, "select two pass log file name prefix", "prefix" },
     { "deinterlace", OPT_EXPERT | OPT_VIDEO, {(void*)opt_deinterlace},