doc/APIchanges: lengthening a hash to make it non ambigous

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

doc/APIchanges

@@ -351,7 +351,7 @@ API changes, most recent first:
 2013-09-04 - 3e1f507 - lavc 55.31.101 - avcodec.h
   avcodec_close() argument can be NULL.
 
-2013-09-04 - 36cd017 - lavf 55.16.101 - avformat.h
+2013-09-04 - 36cd017a - lavf 55.16.101 - avformat.h
   avformat_close_input() argument can be NULL and point on NULL.
 
 2013-08-29 - e31db62 - lavf 55.15.100 - avformat.h