Allow loading data from mat-files that contain other variables

We rely on load_mat_file_data.m from dseries to read in mat-files. There we use

for i=1:length(varlist)
    try
        tmp = getfield(datafile,varlist{i});
        data = [data,  tmp(:)];
    catch
        error(['load_mat_file:: All the vectors (variables) in ' inputname(1) ' must have the same number of rows (observations)!'])
    end
end

to read all variables and concatenate them in an array. If there is any other variable in the mat-file that does not have conformable dimensions, we abort with a crash. This deviates from earlier behavior and will result in many users reporting problems with backward compatibility if we release 4.5 this way. Is there a way to only load the specified varobs? Currently, it seems impossible to pass this through the dseries.