doc/APIchanges: add 2.5 cut marker

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Author: michaelni

doc/APIchanges

@@ -15,6 +15,8 @@ libavutil:     2014-08-09
 
 API changes, most recent first:
 
+-------- 8< --------- FFmpeg 2.5 was cut here -------- 8< ---------
+
 2014-11-21 - ab922f9 - lavu 54.15.100 - dict.h
    Add av_dict_get_string().