Use PIX_FMT_NONE instead of -1 in AVCodec.pix_fmts.

Originally committed as revision 15604 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/libdiracenc.c

@@ -417,6 +417,6 @@ AVCodec libdirac_encoder = {
     libdirac_encode_frame,
     libdirac_encode_close,
    .capabilities= CODEC_CAP_DELAY,
-   .pix_fmts= (enum PixelFormat[]){PIX_FMT_YUV420P, PIX_FMT_YUV422P, PIX_FMT_YUV444P, -1},
+   .pix_fmts= (enum PixelFormat[]){PIX_FMT_YUV420P, PIX_FMT_YUV422P, PIX_FMT_YUV444P, PIX_FMT_NONE},
    .long_name= NULL_IF_CONFIG_SMALL("libdirac Dirac 2.2"),
 } ;