Use AC_ARG_WITH optional args for g-ss detection
Use AC_ARG_WITH optional args for g-ss detection

Use nicer AC_ARG_WITH syntax with optional args to set the
gnome-screensaver prefix.

Signed-off-by: Stephane Delcroix <36bd4f73be32ed7262c164e7ee72163e7543989e@delcroix.org>

Sanva/f-spot,Yetangitu/f-spot,Sanva/f-spot,NguyenMatthieu/f-spot,nathansamson/F-Spot-Album-Exporter,Yetangitu/f-spot,dkoeb/f-spot,GNOME/f-spot,mono/f-spot,GNOME/f-spot,NguyenMatthieu/f-spot,Yetangitu/f-spot,mans0954/f-spot,nathansamson/F-Spot-Album-Exporter,dkoeb/f-spot,GNOME/f-spot,dkoeb/f-spot,mans0954/f-spot,mans0954/f-spot,mono/f-spot,Yetangitu/f-spot,mans0954/f-spot,mono/f-spot,Sanva/f-spot,dkoeb/f-spot,NguyenMatthieu/f-spot,GNOME/f-spot,nathansamson/F-Spot-Album-Exporter,NguyenMatthieu/f-spot,Sanva/f-spot,GNOME/f-spot,NguyenMatthieu/f-spot,mans0954/f-spot,dkoeb/f-spot,mono/f-spot,dkoeb/f-spot,mono/f-spot,Sanva/f-spot,mono/f-spot,Yetangitu/f-spot,mans0954/f-spot,nathansamson/F-Spot-Album-Exporter