make cv::calibrateCamera, cv::stereoCalibrate and their C counterparts return the standard RMS error.

a crash with the libv4l capture code

This was crashing my code:
    for( size_t i = 1; i < imagePoints.size(); i++ )
        objectPoints.push_back(objectPoints[0]);

Changed by:
objectPoints.resize(imagePoints.size(),objectPoints[0]);

Plus clean up on Qt code