Add support for net::accept and net::foreaver and discover a segfault when ending task with left error.
Correct the FUCKING bug that caused a segfault when destructing the either object in the following code:
// g++ -g -std=c++11 test.cpp

int main()
{
    auto callback = []()
    {
        auto either = data::either<std::string,std::vector<int>>(std::string("test"));
        return either;

        if (false)
        {
            return data::either<std::string,std::vector<int>>(std::string("test"));
        }
    };
    callback();
}