avcodec/snow: Make block argumrnt of ff_snow_pred_block() const

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

libavcodec/snow.c

@@ -324,7 +324,7 @@ static void mc_block(Plane *p, uint8_t *dst, const uint8_t *src, int stride, int
     }
 }
 
-void ff_snow_pred_block(SnowContext *s, uint8_t *dst, uint8_t *tmp, ptrdiff_t stride, int sx, int sy, int b_w, int b_h, BlockNode *block, int plane_index, int w, int h){
+void ff_snow_pred_block(SnowContext *s, uint8_t *dst, uint8_t *tmp, ptrdiff_t stride, int sx, int sy, int b_w, int b_h, const BlockNode *block, int plane_index, int w, int h){
     if(block->type & BLOCK_INTRA){
         int x, y;
         const unsigned color  = block->color[plane_index];

libavcodec/snow.h

@@ -231,7 +231,7 @@ void ff_snow_reset_contexts(SnowContext *s);
 int ff_snow_alloc_blocks(SnowContext *s);
 int ff_snow_frame_start(SnowContext *s);
 void ff_snow_pred_block(SnowContext *s, uint8_t *dst, uint8_t *tmp, ptrdiff_t stride,
-                     int sx, int sy, int b_w, int b_h, BlockNode *block,
+                     int sx, int sy, int b_w, int b_h, const BlockNode *block,
                      int plane_index, int w, int h);
 int ff_snow_get_buffer(SnowContext *s, AVFrame *frame);
 /* common inline functions */