Fix up runtime.

Feel free to pull. fmt works, compilers work. Go tool doesn't work. I suspect it has something to do with various system types having improper sizes (see for instance the requisite changes to Stat_t). Is probably a good place for you to hop back in, if you'd like.

And one more note, if you can run cgo with linux emulation, is probably a good idea to run them to autogenerate the proper z-files in pkg/syscall. I suspect that will either fix the go tool or help avoiding problems in the future.