Event as std::variant

[TobiasWallner]

How about we change the class Event into an std::variant?

The way I understand it is that only ever one of the member variables of the Event class will be used at the same time. So we might as well save some memory here by using a variant.

[flagarde]

Std::variant it's c++17 and we would like to be c++11. We can use a union and refactor the event class for this. I tried to do this before but I focused on the more low level stuffs before polishing this

[TobiasWallner]

ok

[TobiasWallner]

and can we have some kind of access operators with const ref and ref access or pointer access with either a std::optional or a pointer returned from a get_if_<type> function (does not need to be templated). I do not want to construct (malloc and copy) an std::string if i can get a reference to it. I would offer it in a pull request and you can see if you like it.

[flagarde]

Same problem this is c++17