File server file copy (INT 21h, F3h - Novell Advanced NetWare 2.0+)

        Entry:
          AH = F3h
          ES:DI -> request string (INT 21h, F3h)
                     WORD  source file handle
                     WORD  destination file handle
                     DWORD starting offset in source
                     DWORD starting offset in destination
                     DWORD number of bytes to copy
        Return:
          AL = status/error code
          CX:DX = number of bytes copied