APIchanges: Add missing entry for SHA-2 512

Signed-off-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

doc/APIchanges

@@ -19,6 +19,13 @@ API changes, most recent first:
 2013-06-05 - fc962d4 - lavu 52.13.0 - mem.h
   Add av_realloc_array and av_reallocp_array
 
+2013-05-30 - 682b227 - lavu 52.35.100
+  Add AVSHA512:
+   av_sha512_alloc()
+   av_sha512_init()
+   av_sha512_update()
+   av_sha512_final()
+
 2013-05-24 - xxxxxxx - lavfi 3.70.100 - avfilter.h
   Add support for slice multithreading to lavfi. Filters supporting threading
   are marked with AVFILTER_FLAG_SLICE_THREADS.