Remove extern C declarations for C++.

FFmpeg is pure C and not all public headers have the declarations.

Originally committed as revision 9037 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavutil/avutil.h

@@ -27,10 +27,6 @@
  */
 
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #define AV_STRINGIFY(s)         AV_TOSTRING(s)
 #define AV_TOSTRING(s) #s
 
@@ -130,8 +126,4 @@ enum PixelFormat {
 #define PIX_FMT_YUV422  PIX_FMT_YUYV422
 #endif
 
-#ifdef __cplusplus
-}
-#endif
-
 #endif /* AVUTIL_H */