Update dimensions in AVCodecContext when RV3/4 frame dimensions change

Originally committed as revision 20572 to svn://svn.ffmpeg.org/ffmpeg/trunk
(cherry picked from commit ec10d2d53999f6edf7d7b5ac88df263eccfb1fb0)

Fixes heap corruption crashes

Addresses: CVE-2011-0722
Signed-off-by: Reinhard Tartler <siretart@tauware.de>
diff --git a/libavcodec/rv34.c b/libavcodec/rv34.c
index c227707..9fe3919 100644
--- a/libavcodec/rv34.c
+++ b/libavcodec/rv34.c
@@ -1247,8 +1247,8 @@
         if(s->width != r->si.width || s->height != r->si.height){
             av_log(s->avctx, AV_LOG_DEBUG, "Changing dimensions to %dx%d\n", r->si.width,r->si.height);
             MPV_common_end(s);
-            s->width  = r->si.width;
-            s->height = r->si.height;
+            s->width  = s->avctx->width  = r->si.width;
+            s->height = s->avctx->height = r->si.height;
             if(MPV_common_init(s) < 0)
                 return -1;
             r->intra_types_hist = av_realloc(r->intra_types_hist, s->b4_stride * 4 * 2 * sizeof(*r->intra_types_hist));