MATLAB R2018b does not have a true batch mode, and will not exit if there is no
final quit statement in a script. Hence ensure there is one when testing a .m
file.
By the way, remove a batch argument for Windows that is obviously incorrect.
If under a Wayland desktop session, some graphics would be displayed on the
screen, despite Octave being run in the virtual X11 frame buffer (xvfb).
Moreover, some unexplained random crashes would occur.
This commit ensures that Wayland is never used when running the testsuite.
By the way, add a command to explain why xvfb-run is needed and the
--no-window-system option cannot be run (see commit
96346b77e5).
Sébastien Villemot