lavc: const correctness for avpicture_fill()

Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavcodec/avcodec.h

@@ -4490,7 +4490,7 @@ void avpicture_free(AVPicture *picture);
  *
  * @see av_image_fill_arrays()
  */
-int avpicture_fill(AVPicture *picture, uint8_t *ptr,
+int avpicture_fill(AVPicture *picture, const uint8_t *ptr,
                    enum AVPixelFormat pix_fmt, int width, int height);
 
 /**

libavcodec/imgconvert.c

@@ -401,7 +401,7 @@ int ff_is_hwaccel_pix_fmt(enum AVPixelFormat pix_fmt)
     return desc->flags & PIX_FMT_HWACCEL;
 }
 
-int avpicture_fill(AVPicture *picture, uint8_t *ptr,
+int avpicture_fill(AVPicture *picture, const uint8_t *ptr,
                    enum AVPixelFormat pix_fmt, int width, int height)
 {
     return av_image_fill_arrays(picture->data, picture->linesize,