Comment 6 for bug 845549

Sorry for the delay, here's a (probably) working patch.

I tested it locally on a clean Xubuntu vm, and it seems to work fine.

I'm not sure how it's going to work with mythbuntu-lightdm-theme, because this package already diverts the greeter conffile. I wanted to test that, but I don't have enough time right now (and I've been already pinged by Robert this morning to post the patch), so it'll stay like this (and the mtyhbuntu developers will have to handle the possible breakage themselves: after all, they choose to implement an ugly and temporary solution instead of pushing for a clean one...).