serenity_dev_
This avoids multiple definition errors when linking software which may utilize these functions from different compilation units.
serenity_dev_{makedev,major,minor}
Add them in `<Kernel/API/Device.h>` and use these to provides `{makedev,major,minor}` in `<sys/sysmacros.h>`. It aims to be more in line with other Unix implementations and avoid code duplication in user land.