Ubuntu PPA updates

[Colin Macdonald]

Hi Mike et al,

How much effort is it to update the Ubuntu stable Octave PPA?  Abhinav 
and I are seeing failures on the Travis Continuous Integration server 
that might be caused by Octave 4.0.0 (and are likely working in 
4.0.1/4.0.2).

If its as easy as pressing a button, please do ;-)  If not, no worries, 
its not essential to get this working.

thanks,
Colin