INT 15 - MultiDOS Plus - REQUEST RESOURCE SEMAPHORE
        AH = 01h
        AL = semaphore number (00h-3Fh)
Return: AH = status
            00h successful
            02h invalid semaphore number
Notes:  if the semaphore is not owned, ownership is assigned to the calling
          task and the call returns immediately
        if the semaphore is already owned by another task, the calling task
          is placed on a queue for the semaphore and suspended until it can
          become owner of the semaphore
        semaphore 0 is used internally by MultiDOS to synchronize DOS access
SeeAlso: AH=10h"MultiDOS",AH=1Bh"MultiDOS"