png decoder use get_buffer, set CODEC_CAP_DR1

Originally committed as revision 19099 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/pngdec.c

@@ -647,7 +647,7 @@ AVCodec png_decoder = {
     NULL,
     NULL, //decode_end,
     decode_frame,
-    0 /*CODEC_CAP_DR1*/ /*| CODEC_CAP_DRAW_HORIZ_BAND*/,
+    CODEC_CAP_DR1 /*| CODEC_CAP_DRAW_HORIZ_BAND*/,
     NULL,
     .long_name = NULL_IF_CONFIG_SMALL("PNG image"),
 };