vlc_es: add ICC profile struct

We store the ICC profile as part of the (ancillary) data allocation,
using a trailing unsized array. This is because we need to copy it in
and out of various libraries anyway, to avoid having to expose things
like AVBufferRef.

The (as of writing) current ICC specification can be found at
https://www.color.org/specification/ICC.1-2022-05.pdf

include/vlc_es.h

@@ -601,6 +601,18 @@ typedef struct vlc_video_dovi_metadata_t
     } nlq[3];
 } vlc_video_dovi_metadata_t;
 
+/**
+ * Embedded ICC profiles
+ */
+
+#define VLC_ANCILLARY_ID_ICC VLC_FOURCC('i','C','C','P')
+
+typedef struct vlc_icc_profile_t
+{
+    size_t size;
+    uint8_t data[]; /* binary profile data, see ICC.1:2022 (or later) */
+} vlc_icc_profile_t;
+
 /**
  * subtitles format description
  */