hpaned in file selection

[Tim Janik <timj gtk org>]

hey all,

we changed the file selection dialog so that the two
list views are inside a horizontal paned widget now.
this is a major aid for searching through lists of
long file names (e.g. lots of Singer-(Album)-SongTitle.ogg
files) which won't fit into the file list display even
if the whole dialog is fullscreened (due to the default
expand packing, the filename list can only take up half
the window width).

though we don't expect any real world breakage from adding
a hpaned to the widget ancestry, we meant to give a heads
up about the change because the FS has been know to be lots
of fooled around with in third-party applications. (though,
people who add widgets to it should really constrain
changes to the ->action_area which is not affected).

---
ciaoTJ