Revert:

r18826 | stefano | 2009-05-14 20:50:58 +0200 (Thu, 14 May 2009) | 2 lines
	Make av_set_string3() print a message in case of unknown option.

This change led to multiple identical error messages to be printed if an option
was not found.

Originally committed as revision 20172 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/opt.c

@@ -112,10 +112,8 @@ int av_set_string3(void *obj, const char *name, const char *val, int alloc, cons
     const AVOption *o= av_find_opt(obj, name, NULL, 0, 0);
     if (o_out)
         *o_out = o;
-    if(!o) {
-        av_log(obj, AV_LOG_ERROR, "Unknown option '%s'\n", name);
+    if(!o)
         return AVERROR(ENOENT);
-    }
     if(!val || o->offset<=0)
         return AVERROR(EINVAL);