Replace _set_at2 by _get_at for array.

(Break API)

example/ex-multi01.c

@@ -47,8 +47,8 @@ static void program_init(program_t p, string_t text) {
         int left;
         array_int_pop_back(&left, leftstack);
         int right = pc;
-        array_int_set_at2 (p->bracket_map, left, right);
-        array_int_set_at2 (p->bracket_map, right, left);
+        *array_int_get_at (p->bracket_map, left) = right;
+        *array_int_get_at (p->bracket_map, right) = left;
       }
 
     pc++;