This time I used mkusb to create a 'clean' boot drive. Now there is an option to auto-resize:
'Installera Lubuntu 15.10 vid sidan av Ubuntu 14.04.2 LTS' which translates to 'Install alongside'
-o-
It seems that the problem was that I booted the installer via grub2 and the iso file: 'grub-n-iso', which seems to have confused the alternatives of the installer.
This time I used mkusb to create a 'clean' boot drive. Now there is an option to auto-resize:
'Installera Lubuntu 15.10 vid sidan av Ubuntu 14.04.2 LTS' which translates to 'Install alongside'
-o-
It seems that the problem was that I booted the installer via grub2 and the iso file: 'grub-n-iso', which seems to have confused the alternatives of the installer.