Heads-up: overwrite confirmation for GtkFileChooser

[Federico Mena Quintero <federico ximian com>]

Hi,

I just implemented overwrite confirmation for the file chooser.  You
have to enable this feature explicitly, to keep compatibility with
applications that already pop up their custom confirmation dialogs.
Please read this blog entry for the details:

http://primates.ximian.com/~federico/news-2005-07.html#14

Let's try to keep apps in 2.12 consistent by using this little feature.
Whoever uses it last gets to buy beer for all the rest at the next
GUADEC :)

  Federico