Screen: Add DC-1394 videocapture device enumeration.

Enumerate libdc1394 supported cameras on the Firewire
bus and provide info like vendor, model, guid, unit-id
in a format similar to GStreamer engines format.

-> Screen for 64-Bit Octave on Linux rebuilt and tested with
   3 connected cameras.

-> Modified VideoMultiCameraCaptureDemo.m so that it can auto-
   detect and use all enumerated cameras.