Changelog/APIChanges Put 3.0 release marker

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

Changelog

@@ -2,6 +2,9 @@ Entries are sorted chronologically from oldest to youngest within each release,
 releases are sorted from youngest to oldest.
 
 version <next>:
+
+
+version 3.0:
 - Common Encryption (CENC) MP4 encoding and decoding support
 - DXV decoding
 - extrastereo filter

doc/APIchanges

@@ -15,6 +15,8 @@ libavutil:     2015-08-28
 
 API changes, most recent first:
 
+-------- 8< --------- FFmpeg 3.0 was cut here -------- 8< ---------
+
 2016-02-10 - bc9a596 / 9f61abc - lavf 57.25.100 / 57.3.0 - avformat.h
   Add AVFormatContext.opaque, io_open and io_close, allowing custom IO