cbs_mpeg2: Decompose Sequence End

Sequence End units (or actually, sequence_end_codes) have up until now
not been decomposed; in fact due to a bug in cbs_mpeg2_split_fragment they
have mostly been treated as part of the preceding unit. So implement
decomposing them as preparation for fixing said bug.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

libavcodec/cbs_mpeg2_syntax_template.c

@@ -411,3 +411,15 @@ static int FUNC(slice_header)(CodedBitstreamContext *ctx, RWContext *rw,
 
     return 0;
 }
+
+static int FUNC(sequence_end)(CodedBitstreamContext *ctx, RWContext *rw,
+                              MPEG2RawSequenceEnd *current)
+{
+    int err;
+
+    HEADER("Sequence End");
+
+    ui(8, sequence_end_code);
+
+    return 0;
+}