avfilter/internal: Don't include framepool.h, thread.h

They are not used by the header at all and only used by very few files;
so include the headers in their users instead of in internal.h.

Reviewed-by: Nicolas George <george@nsup.org>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavfilter/internal.h

@@ -27,9 +27,7 @@
 #include "libavutil/internal.h"
 #include "avfilter.h"
 #include "formats.h"
-#include "framepool.h"
 #include "framequeue.h"
-#include "thread.h"
 #include "version.h"
 #include "video.h"
 #include "libavcodec/avcodec.h"