avcodec/internal: Move FF_CODEC_CAP_* to a new header codec_internal.h

Also move FF_CODEC_TAGS_END as well as struct AVCodecDefault.
This reduces the amount of files that have to include internal.h
(which comes with quite a lot of indirect inclusions), as e.g.
most encoders don't need it. It is furthemore in preparation
for moving the private part of AVCodec out of the public codec.h.

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

libavcodec/eatgv.c

@@ -34,6 +34,7 @@
 #define BITSTREAM_READER_LE
 #include "avcodec.h"
 #include "get_bits.h"
+#include "codec_internal.h"
 #include "internal.h"
 
 #define EA_PREAMBLE_SIZE    8