Localisation with .po files

[GijsTimmers]

Request: implement .po translation files

[jovanbulck]

Ok would be cool indeed. This change will require some effort however: changing the code to call gettext whenever some string is outputed and then also of course translating those strings...

I don't have any expierence with gettext yet, so I'll need some time fist to get familiar with the process. I just had a quick look and it looks all right. From a security point of view, it's of major importance to avoid format string vulnerabilities caused by translating format strings. This can be achieved by marking the format string with xgettext:c-format in the code, I see.