Bug#581873: [languagechooser] unable to select language more than once

[Frans Pop <elendil@planet.nl>]

> *Exactly* when did you do this? I suspect it was after the step of
> loading additional components? Before that point changing the language
> should work fine. After that point the language setting *is* changed,
> but you get English because other translations have been deleted to save
> memory.

I've committed a change in rootskel so that translations only get dropped 
if the system has less than 250MB RAM. If we could display the dialog 
saying that changing the language is no longer possible that would 
probably not be needed, but since that does not work I think it's better 
to just keep translations when possible.