vboxdrv setup fails at compiling modules

Hello,

I have recently upgraded from 13.04, where everything worked fine, to 13.10, where I cannot get VirtualBox to work any more.
I did some googling but could not find a similar error (all involved explicit compilation issue against bad headers for example, but there seems to be nothing of the like in my situation?).

When trying to setup VirtualBox, I get the following:
Here are the logs:
vbox-install.log: http://pastebin.com/6G2awxR5
make.log: http://pastebin.com/BTXhMGgQ

Looking at neither of the mentioned logs revealed nothing useful to me. It seems that the .ko files are not getting generated which prevents the whole operation.
I have been trying both the "virtualbox" package of the ubuntu saucy repository:
And the "virtualbox-4.3" package of the specific virtualbox repository:
...but both failed with the same errors.

I am currently running kernel 3.11.0-15:
Can I please get some help as to how solve this? How would you go about investigating this build issue? I have tried making my way in the Makefiles but it got complicated quite quickly and I'm sure I missed something obvious.

Thanks a lot!