first pass at ALAC decoder from David Hammerton; while David's original

decoder works great, this decoder is not completely and seamlessly
integrated yet with FFmpeg

Originally committed as revision 4008 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/allcodecs.c

@@ -196,6 +196,7 @@ void avcodec_register_all(void)
     register_avcodec(&qtrle_decoder);
     register_avcodec(&flac_decoder);
     register_avcodec(&shorten_decoder);
+    register_avcodec(&alac_decoder);
 #endif /* CONFIG_DECODERS */
 
 #ifdef AMR_NB