proresenc_kostya: Mention likely ancestry in the license header.

As the encoder contained the same bug and has similar structure
to anatoliys encoder, it is possibly based on it.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/proresenc_kostya.c

@@ -3,6 +3,9 @@
  *
  * Copyright (c) 2012 Konstantin Shishkov
  *
+ * This encoder appears to be based on Anatoliy Wassermans considering
+ * similarities in the bugs.
+ *
  * This file is part of Libav.
  *
  * Libav is free software; you can redistribute it and/or