svq1dec: call avcodec_set_dimensions() after dimensions changed.

Fixes NGS00148, CVE-2011-4579

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

(cherry picked from commit 6e24b9488e)

Signed-off-by: Reinhard Tartler <siretart@tauware.de>
(cherry picked from commit 0eca0da06e)

Signed-off-by: Reinhard Tartler <siretart@tauware.de>
(cherry picked from commit 8ddc0b491d)

Signed-off-by: Reinhard Tartler <siretart@tauware.de>

libavcodec/svq1dec.c

@@ -676,6 +676,7 @@ static int svq1_decode_frame(AVCodecContext *avctx,
 #endif
     return result;
   }
+  avcodec_set_dimensions(avctx, s->width, s->height);
 
   //FIXME this avoids some confusion for "B frames" without 2 references
   //this should be removed after libavcodec can handle more flexible picture types & ordering