ffmpeg: look for encoding options in both avcodec and avformat

This patch is the same as 8a1714ad85 but
applied to encoding. It fixes the current clash of the -password option
between tta decoder and the icecast protocol.

ffmpeg_opt.c

@@ -2014,8 +2014,13 @@ loop_end:
         const AVClass *class = avcodec_get_class();
         const AVOption *option = av_opt_find(&class, e->key, NULL, 0,
                                              AV_OPT_SEARCH_CHILDREN | AV_OPT_SEARCH_FAKE_OBJ);
-        if (!option)
+        const AVClass *fclass = avformat_get_class();
+        const AVOption *foption = av_opt_find(&fclass, e->key, NULL, 0,
+                                              AV_OPT_SEARCH_CHILDREN | AV_OPT_SEARCH_FAKE_OBJ);
+        if (!option || foption)
             continue;
+
+
         if (!(option->flags & AV_OPT_FLAG_ENCODING_PARAM)) {
             av_log(NULL, AV_LOG_ERROR, "Codec AVOption %s (%s) specified for "
                    "output file #%d (%s) is not an encoding option.\n", e->key,