!!!!! add critical section handling !!!!!!!

- add a verify_area(VERIFY_READ,data, size) or ..VERIFY_WRITE..
  #include <asm/uaccess.h>

- implement an ioctl that waits for a number of dmx-frames passed
  or sends a signal for each dmx-frame that has been passed.

- add support for rtai
  #ifdef CONFIG_KERNEL_HAS_RTAI
  // ON_KERNEL_HAS_RTAI(x)
