darwinkit: fill out placeholder structs

[progrium]

We don't yet generate structs. Part of the reason for this is we need to match the data alignment of the structs they represent, and we have everything but what order the fields are. In order to get current frameworks to generate, I have created placeholder structs in the <framework>_structs.go file for frameworks that are empty of fields. Somebody needs to go and check out their actual full declaration in the framework header files and port their fields to Go fields. Perhaps in the process find a way to automate this.