lavc/libutvideoenc: Cast an unsigned constant to int.

Fixes the following warning / error:
libavcodec/libutvideoenc.cpp:281:1: warning: narrowing conversion of ‘3221258240u’ from ‘unsigned int’ to ‘int’ inside { } is ill-formed in C++11 [-Wnarrowing]

Fixes ticket #5542.

libavcodec/libutvideoenc.cpp

@@ -254,7 +254,7 @@ AVCodec ff_libutvideo_encoder = {
     NULL_IF_CONFIG_SMALL("Ut Video"),
     AVMEDIA_TYPE_VIDEO,
     AV_CODEC_ID_UTVIDEO,
-    AV_CODEC_CAP_AUTO_THREADS | AV_CODEC_CAP_LOSSLESS | AV_CODEC_CAP_INTRA_ONLY,
+    AV_CODEC_CAP_AUTO_THREADS | (int)AV_CODEC_CAP_LOSSLESS | AV_CODEC_CAP_INTRA_ONLY,
     NULL, /* supported_framerates */
     (const enum AVPixelFormat[]) {
         AV_PIX_FMT_YUV420P, AV_PIX_FMT_YUYV422, AV_PIX_FMT_BGR24,