alacenc : Report supported input sample formats.

Originally committed as revision 22829 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/alacenc.c

@@ -528,5 +528,6 @@ AVCodec alac_encoder = {
     alac_encode_frame,
     alac_encode_close,
     .capabilities = CODEC_CAP_SMALL_LAST_FRAME,
+    .sample_fmts = (const enum SampleFormat[]){ SAMPLE_FMT_S16, SAMPLE_FMT_NONE},
     .long_name = NULL_IF_CONFIG_SMALL("ALAC (Apple Lossless Audio Codec)"),
 };