vm overcommit handling

[Wolfgang Spraul]

David,

> Would be nice to add it in a place that effects config.minimal as well
> as config.full_system.  I want my config.minimal images to be able to
> run Octave out-of-the-box.

Sounds good to me, not sure about the best place to add it, maybe
Xiangfu can give us advice.

Very well researched improvement, thanks a lot!
Wolfgang