TODO-kernel

- setuid/setgid must effect process
  + test syscalls (getuid) afterwards
  + test core file content

  + use UID/GID in access(2), chmod(2), chown(2), link(2)

- nice level is process property

- rlimit should be process-wide and SIGXCPU should be sent if all threads
  together exceed the limit

- getrusage() must return resource utilization for the process



The following are possible optimizations and in no way required:


- the scheduler should be thread group-aware, i.e., it has to give time to
  the thread group not proportional to the number of threads.