Remove useless definition of struct AVCLASS.

Originally committed as revision 19402 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavutil/log.h

@@ -29,8 +29,7 @@
  * arbitrary struct of which the first field is a pointer to an
  * AVClass struct (e.g. AVCodecContext, AVFormatContext etc.).
  */
-typedef struct AVCLASS AVClass;
-struct AVCLASS {
+typedef struct {
     /**
      * The name of the class; usually it is the same name as the
      * context structure type to which the AVClass is associated.
@@ -49,7 +48,7 @@ struct AVCLASS {
      * @see av_set_default_options()
      */
     const struct AVOption *option;
-};
+} AVClass;
 
 /* av_log API */