Semaphore resources can only be freed if the semaphore is not locked.  A
public semaphore should first be removed from the system semaphore list
with the RemSemaphore() function. This prevents other tasks from finding
the semaphore and trying to lock it. Once the semaphore is removed from
the system list, the semaphore should be locked exclusively so no other
task can lock it.  Once the lock is obtained, it can be released again,
and the resources can be deallocated.

The following code should be used to remove a public semaphore:

    UBYTE *name;
    struct SignalSemaphore *semaphore;

    Forbid();
    if (semaphore=FindSemaphore(name))
    {
        RemSemaphore(semaphore);       /* So no one else can find it... */
        ObtainSemaphore(semaphore);    /* Wait for us to be last user...*/
        ReleaseSemaphore(semaphore);   /* Ready for cleanup...          */
    }
    FreeMem(semaphore, sizeof(struct SignalSemaphore));
    Permit();