fixes these test failures in ASAN builds (in 10.1 and 10.4):
* main.signal_demo3
* main.sp
* sys_vars.max_sp_recursion_depth_func
* mroonga/storage.foreign_key_delete_existent
* mroonga/storage.foreign_key_delete_nonexistent
* mroonga/storage.foreign_key_insert_existent
* mroonga/storage.foreign_key_update_existent
* mroonga/storage.foreign_key_update_nonexistent
* mroonga/storage.function_command_auto-escape
* mroonga/storage.function_command_select
* mroonga/storage.variable_enable_operations_recording_insert