The posix wrapper do not have a fixed posix standard.

## Brief feature description

During the implementation of the `UnnamedSemaphore` we discovered that the man page, as well as the documentation from opengroup differ. See the docu for `sem_init`
* https://pubs.opengroup.org/onlinepubs/9699919799/functions/sem_init.html
* https://man7.org/linux/man-pages/man3/sem_init.3.html

Those implementations have different `errno` codes and other posix functions may differ in their behavior.

We have to define a POSIX standard which is required for all posix wrappers, provide a link to the corresponding documentation of a specific posix wrapper and adjust the wrapper accordingly if they differ from their expected behavior.

Start by comparing the POSIX sem_init specification at the Open Group with the Linux man page, as described in the issue and discovered during UnnamedSemaphore implementation. Inventory the POSIX wrappers and their current behavior, then define the required POSIX standard, link each wrapper to its reference documentation, and align differences with the expected behavior.

Written by the indexing model from the issue text.