Some documentation

Rev: src/modules/system/doc/getegid:1.1
Rev: src/modules/system/doc/geteuid:1.1
Rev: src/modules/system/doc/getgid:1.1
Rev: src/modules/system/doc/getpgrp:1.1
Rev: src/modules/system/doc/getpid:1.1
Rev: src/modules/system/doc/getppid:1.1
Rev: src/modules/system/doc/getuid:1.1
Rev: src/modules/system/doc/hardlink:1.1
Rev: src/modules/system/doc/initgroups:1.1
Rev: src/modules/system/doc/readlink:1.1
Rev: src/modules/system/doc/setegid:1.1
Rev: src/modules/system/doc/seteuid:1.1
Rev: src/modules/system/doc/setgid:1.1
Rev: src/modules/system/doc/setuid:1.1
Rev: src/modules/system/doc/symlink:1.1