[Gimp-developer] Automaticly append file extensions when exporting

[john silver <brckbrd yahoo com>]

The program should automaticly append the file extensions when exporting. If you export it as a PNG then the 
.PNG extension should be tacked on the end. If you try to manually change the extension to something 
different then the file type like trying to save a JPG format with a .PNG extension then the program should 
give you a warning message and ask if you are sure you want to do that.