Add some pre-generated MIG headers
Reason: CMake's dependency scanner doesn't detect that some of the headers are generated and it doesn't try to generate them for other targets that depend on them indirectly (e.g. libc) and therefore parallel builds will fail.
The temporary solution is to check-in the generated headers into the source (just like we were doing before in `platform-include`). The proper solution would be to manually add dependencies for each target that needs the headers (which is pretty much *everything*), but that's ridiculous. Honestly, CMake should be able to detect this on its own, but whatever; this is a workaround.