[plt-dev] language dialog

I found some bugs in the way the language dialog is set up (these are
ripples from earlier fixes to the language dialog that introduced the
bug that caused the module language to forget the collection paths
...). If you have time, please do poke around in that dialog and see
if you can get strange things to happen ... (I'm trying too and so far
everything is okay, afaict.) Note that I just committed a fix
(revision 14164).

Thanks,
Robby