Added arginfos and tweaked function declarations to be compatible with PHP8

posix_semaphores.stub.php

@@ -0,0 +1,11 @@
+<?php
+
+function posix_sem_open(string $name, int $flags, int $mode, int $value) : resource|null {}
+function posix_sem_close(resource $semaphore) : boolean {}
+function posix_sem_unlink(resource $semaphore) : boolean {}
+function posix_sem_post(resource $semaphore) : boolean {}
+function posix_sem_wait(resource $semaphore) : boolean {}
+function posix_sem_trywait(resource $semaphore) : boolean {}
+function posix_sem_timedwait(resource $semaphore, int $timeout_sec, int $timeout_nsec = 0) : boolean {}
+function posix_sem_getvalue(resource $semaphore) : int|null {}
+function posix_sem_error() : int {}