Move declaration of prn before any assignment.

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@18255 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavcodec/snow.c

@@ -4698,9 +4698,9 @@ int main(void){
     int buffer[2][width*height];
     SnowContext s;
     int i;
+    AVLFG prn;
     s.spatial_decomposition_count=6;
     s.spatial_decomposition_type=1;
-    AVLFG prn;
 
     av_lfg_init(&prn, 1);