Bug #176 - Support newer versions of FFmpeg.

Also includes Benjamin's ffmpeg-configure-v2.patch.

lib-src/ffmpeg/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 +48,15 @@ struct AVCLASS {
      * @see av_set_default_options()
      */
     const struct AVOption *option;
-};
+
+    /**
+     * LIBAVUTIL_VERSION with which this structure was created.
+     * This is used to allow fields to be added without requiring major
+     * version bumps everywhere.
+     */
+
+    int version;
+} AVClass;
 
 /* av_log API */