Implement without having code in the start section

[notgull]

@kchibisov suggested that the error handling mechanism could be implemented without having code in ctor. Right now the implementation needs the default error hook's value so we can compare for it in the X11 error handler. Calling the default error hook isn't an option, since the default error hook exits the entire process.

[kchibisov]

The suggestion is to put your error hook inside the users error hook and ask the user to provide a way to do so, we do this thing in glutin for what it worth.

[notgull]

The suggestion is to put your error hook inside the users error hook and ask the user to provide a way to do so,

The way this is done in glutin is unsound, I believe.

[kchibisov]

In which way it's unsound? it can be accessed only by one thread at a time, nothing deals with C lib, and the hook disables itself once it's not in use.

It's true that the error may arrive a lot later, but due to the specifics of how mesa calls glutin, as in, there's never a x11 communication in the first place, I'm not sure there's any issue with it.