[gtkada] Bug in Gdk.Pixbuf.Save

[Arnaud Charlet]

> Here's a fix, without it you'll get segmentation faults.

Thanks for the fix. Interestingly, I was playing with this function myself
and discovered the problem at about the same time you reported the fix :-)

> It would be useful to mention in the spec under procedures
> Gdk_New_From_File and Save that the Error parameter is not
> set if no error occurred.

Spec has been updated and patch incorporated.

Arno