build/win32/vs10/gengir.vcxproj: Add PlatformToolset tag
build/win32/vs10/gengir.vcxproj: Add PlatformToolset tag

This makes it easier to upgrade to Visual Studio 2012/2013 formats,
like the other *.vcxproj files in GDK-Pixbuf.

GNOME/gdk-pixbuf,GNOME/gdk-pixbuf,GNOME/gdk-pixbuf,YueLinHo/MB3Gdk-pixbuf,Distrotech/gdk-pixbuf,YueLinHo/MB3Gdk-pixbuf,Distrotech/gdk-pixbuf,Distrotech/gdk-pixbuf,GNOME/gdk-pixbuf,Distrotech/gdk-pixbuf,YueLinHo/MB3Gdk-pixbuf,YueLinHo/MB3Gdk-pixbuf,YueLinHo/MB3Gdk-pixbuf,Distrotech/gdk-pixbuf