branches/zip: mem_area_free(): Correct a bug that was introduced in r4088.

free() is not the same as ut_free().  ut_free() pairs with ut_malloc(),
not malloc().  free() pairs with malloc() and some other functions.

mem/mem0pool.c

@@ -478,7 +478,7 @@ mem_area_free(
 	ulint		n;
 
 	if (srv_use_sys_malloc) {
-		ut_free(ptr);
+		free(ptr);
 
 		return;
 	}