v4l2 update function, video source size change, "check" unit test system integration

This part of the project on dynamic change the resolution depending on the quality of the communication channel. v4l can change resolution of the cam, so, i think this is a useful feature.
the "size" parameter is already part of vidsrc_alloc and will most likely confuse
the users. perhaps it is better to add it to the function signature itself?