lavu: keep context size variables

They are essential to be able to use the utils without av_malloc()
That is for example use with malloc(), memalign(), some other
private allocation function, on the stack or others.

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

libavutil/tree.c

@@ -28,9 +28,7 @@ typedef struct AVTreeNode {
     int state;
 } AVTreeNode;
 
-#if FF_API_CONTEXT_SIZE
 const int av_tree_node_size = sizeof(AVTreeNode);
-#endif
 
 struct AVTreeNode *av_tree_node_alloc(void)
 {