structure: CAvl: add missing undef

structure/CAvl_footer.h

@@ -32,6 +32,7 @@
 #undef CAVL_PARAM_ENTRY
 #undef CAVL_PARAM_LINK
 #undef CAVL_PARAM_KEY
+#undef CAVL_PARAM_ARG
 #undef CAVL_PARAM_COUNT
 #undef CAVL_PARAM_COUNT_MAX
 #undef CAVL_PARAM_NULL