video(1) uses mmap and ioctls by default, those ioctls only work on
video(4) devices. If -i is passed, use read(2) instead of the mmap(2)
routines, instead of requiring the user to pass also pass the -g flag.
and display the frame rates if at least on -v is used.
* set/get the video(4) device's frame rate using VIDIOC_{S,G}_PARM.
* add new option -R which dsables frame rate adjustment. only really
useful for video(4) devices, to see the difference between the frame
rate the device generates and what it says it's configured for ...
many devices don't generate the rate they are configured if they
aren't getting enough light ...
* poll(2) input with INFTIM instead of 0 timeout, and handle the poll(2)
call being interrupted by the frame timer.
* only use usleep(3) to wait for frames if the input is a file, and
in that case, sleep for a full frame interval or until interrupted
by the frame timer.
* update the manual to describe the new -R option, that -r now sets
video(4) frame rate, and that at least one -v will display supported
properties of the hardware.
