Add an APIchanges entry for av_register_protocol2

Originally committed as revision 23703 to svn://svn.ffmpeg.org/ffmpeg/trunk

doc/APIchanges

@@ -12,6 +12,9 @@ libavutil:   2009-03-08
 
 API changes, most recent first:
 
+2010-06-22 - r23702 - lavf 52.69.0 - av_register_protocol2
+  Add av_register_protocol2(), deprecating av_register_protocol()
+
 2010-06-09 - r23551 - lavu 50.19.0 - av_compare_mod()
   Add av_compare_mod() to libavutil/mathematics.h.