VideoOfflineCaptureDemo.m: White-space / indentation cleanup.
Screen/GStreamer: Handle video sources with range of valid width x height.

Some framegrabbers return width and height of valid capture resolutions
not as fixed width x height pairs (one per cap), but for each cap as a
range of valid values, e.g., analog framegrabbers for connecting fMRI
compatible analog cameras. Modify matching logic to deal with it.

The whole auto-detection of suitable resolutions and framerates is
still a fragile thing on different cameras, as many cameras apparently
lie about their truly supported caps, or fail to mention restrictions
and caveats to the capture framework. A little sampling:

- The 2010 MBP iSight automagically works.

- The analog -> digital USB framegrabber thingy automagically works.

- The Logitech Cxxx USB webcam detects correct framerate but auto-selects
  a too high default resolution, which it then can't handle, so manual
  selection of a lower override resolution is required.

- The Sony PlayStation Eye 3 camera selects too high framerates - and hangs -
  if the 'realmax' value for fps auto-detection is used. It also hangs whenever
  no manual resolution is specified, although it auto-detects the correct
  resolution. The latter failure due to taking a different setup code path,
  which sets different basic colorcaps in auto-detect vs. manual override.
  Also it lies about what max fps it can handle at specific resolutions, so
  one has to find out by trial and error which combos of resolution and fps
  work. E.g., 320x240 works at up to 125 fps. 640x480 only works up to 30 fps,
  although the camera claims it can do 60 fps - and then malfunctions if one
  tries. Probably the 60 fps at 640x480 mode only works for special color
  caps settings which the cam fails to mention properly to the capture engine.

-> Sometimes there's just no winning. Reliable videocapture without manual
   parameter tweaking just seems to be against some law of nature.

-> Screen for 64-Bit Octave on Linux rebuilt and tested with above cams with
   above results.