In those releases, the intersect function was behaving differently when given
arguments with different orientations.
Put the two arguments in the same orientation, to avoid the problem (recalling
that options_.varobs is column-oriented).
If the m data file is in the current directory, the first output of
fileparts(options_.datafile) is an empty string. In Matlab the command
cd('') fails, but Octave does not fail in this case (and does nothing).
Added a test on the first output of fileparts, if this output is empty
we do not try to change the current directory.