Bugfix: Problems exposed by f_thread unit tests.

Bugfix: Problems exposed by f_thread unit tests.

Notable fixes:
- Rename f_thread_semaphore_file_create() to f_thread_semaphore_file_open().
- Rename f_thread_semaphore_file_delete() to f_thread_semaphore_file_close().
- Rename f_thread_semaphore_file_destroy() to f_thread_semaphore_file_delete().
- Have f_thread_semaphore_file_open() accept a double pointer for semaphore because sem_open() returns a pointer.
- Initializer f_thread_semaphore_t_initialize is on a union which is initialized differently from a normal digit.