lavfi/apad: switch to AVOption-based system

libavfilter/af_apad.c

@@ -144,8 +144,6 @@ static const AVFilterPad apad_outputs[] = {
     { NULL },
 };
 
-static const char *const shorthand[] = { NULL };
-
 AVFilter avfilter_af_apad = {
     .name          = "apad",
     .description   = NULL_IF_CONFIG_SMALL("Pad audio with silence."),
@@ -154,5 +152,4 @@ AVFilter avfilter_af_apad = {
     .inputs        = apad_inputs,
     .outputs       = apad_outputs,
     .priv_class    = &apad_class,
-    .shorthand     = shorthand,
 };

libavfilter/avfilter.c

@@ -658,6 +658,7 @@ int avfilter_init_filter(AVFilterContext *filter, const char *args, void *opaque
     int anton_options =
         !strcmp(filter->filter->name,  "afade"     ) ||
         !strcmp(filter->filter->name,  "aformat") ||
+        !strcmp(filter->filter->name,  "apad"      ) ||
         !strcmp(filter->filter->name,  "ass")     ||
         !strcmp(filter->filter->name,  "blackframe") ||
         !strcmp(filter->filter->name,  "blend"     ) ||