avcodec/huffyuv: add a field that represents the number of symbols

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

libavcodec/huffyuv.h

@@ -68,6 +68,7 @@ typedef struct HYuvContext {
     int yuy2;                               //use yuy2 instead of 422P
     int bgr32;                              //use bgr32 instead of bgr24
     int bps;
+    int n;                                  // 1<<bps
     int alpha;
     int chroma;
     int yuv;