Move member to improve struct alignment.

src/xt_idxsection.c

@@ -149,11 +149,11 @@ struct Xt_idxsection_ {
 
   struct Xt_idxlist_ parent;
 
+  Xt_int *index_array_cache;
+
   Xt_int global_start_index;
   Xt_int local_start_index;
 
-  Xt_int *index_array_cache;
-
   Xt_int min_index_cache;
   Xt_int max_index_cache;
   int ndim;