sem_open()
sem_unlink()
sem_close()
Implements `sem_open()`, `sem_unlink()` & `sem_close()` functions and added tests for them. Updated existing tests and POSIX docs. Signed-off-by: Yong Cong Sin <ycsin@meta.com>
This change is setting up for switching over to proper POSIX option requirements, feature test macros, and a dependency structure that is reflective of the standard. Signed-off-by: Christopher Friedt <cfriedt@meta.com>