lavfi/video: fix copyright

git blame:
    132 Stefano Sabatini
     77 Vitor Sessak
     49 Michael Niedermayer
     24 Anton Khirnov
     22 S.N. Hemanth Meenakshisundaram
     13 Bobby Bingham
      7 Luca Barbato
      2 Nicolas George
      2 Alex Converse
      1 Diego Elio Pettenò

Initial commit not traced as this file was split out.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavfilter/video.c

 /*
+ * Copyright 2007 Bobby Bingham
+ * Copyright Stefano Sabatini <stefasab gmail com>
+ * Copyright Vitor Sessak <vitor1001 gmail com>
+ *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or