cmdutils: make the "-help filter=" output less confusing

Example:
Filter overlay
  Overlay a video source on top of the input.
    Inputs:
       #0: main (video)
       #1: overlay (video)
    Outputs:
       #0: default (video)
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

cmdutils.c

@@ -1661,7 +1661,7 @@ static void show_help_filter(const char *name)
     printf("    Inputs:\n");
     count = avfilter_pad_count(f->inputs);
     for (i = 0; i < count; i++) {
-        printf("        %d %s (%s)\n", i, avfilter_pad_get_name(f->inputs, i),
+        printf("       #%d: %s (%s)\n", i, avfilter_pad_get_name(f->inputs, i),
                media_type_string(avfilter_pad_get_type(f->inputs, i)));
     }
     if (f->flags & AVFILTER_FLAG_DYNAMIC_INPUTS)
@@ -1672,7 +1672,7 @@ static void show_help_filter(const char *name)
     printf("    Outputs:\n");
     count = avfilter_pad_count(f->outputs);
     for (i = 0; i < count; i++) {
-        printf("        %d %s (%s)\n", i, avfilter_pad_get_name(f->outputs, i),
+        printf("       #%d: %s (%s)\n", i, avfilter_pad_get_name(f->outputs, i),
                media_type_string(avfilter_pad_get_type(f->outputs, i)));
     }
     if (f->flags & AVFILTER_FLAG_DYNAMIC_OUTPUTS)