Changelog: Add cropdetect non 8bpp

Suggested-by: Reimar
Previous patch reviewed-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Changelog

@@ -9,6 +9,7 @@ version <next>:
 - RTP/mpegts muxer
 - non continuous cache protocol support
 - tblend filter
+- cropdetect support for non 8bpp, absolute (if limit >= 1) and relative (if limit < 1.0) threshold
 
 
 version 2.5: