no change.
* fixed the bug class `result_set’ inherit unknown class `result_set_flag’.
* regarding the template-specialized class `result_set<void>’ and `result_set<>’ as typedefed `void’.
* added template-specialized class `boost::optional<void>’. it expresses `void’.
* I gave up implementing class `functor’ in ver 1.0 release. I can’t solve the type-associated problems.
* I rewrite the file.
* comment out the code about class `functor’.