ffprobe: show probe_score in the format section

Should address trac ticket #2621.

doc/ffprobe.xsd

@@ -185,6 +185,7 @@
       <xsd:attribute name="duration"         type="xsd:float"/>
       <xsd:attribute name="size"             type="xsd:long"/>
       <xsd:attribute name="bit_rate"         type="xsd:long"/>
+      <xsd:attribute name="probe_score"      type="xsd:int"/>
     </xsd:complexType>
 
     <xsd:complexType name="tagType">

ffprobe.c

@@ -1867,6 +1867,7 @@ static void show_format(WriterContext *w, AVFormatContext *fmt_ctx)
     else           print_str_opt("size", "N/A");
     if (fmt_ctx->bit_rate > 0) print_val    ("bit_rate", fmt_ctx->bit_rate, unit_bit_per_second_str);
     else                       print_str_opt("bit_rate", "N/A");
+    print_int("probe_score", av_format_get_probe_score(fmt_ctx));
     show_tags(w, fmt_ctx->metadata, SECTION_ID_FORMAT_TAGS);
 
     writer_print_section_footer(w);