Continued some #GObject subclassing support in Go. Turns out I messed up the C memory alignment in #Go for and ended up embedding the parent class as a reference, when GObject expects it to be the actual struct. Funnily enough some callbacks still worked before this, but now even the ones like `Snapshot` and `Activate` work. To demonstrate, here is a Go application subclassing AdwApplication and overwriting the `activate` callback instead of calling `ConnectCallback`!