pixops: Special-case compositing/copying with no scaling
pixops: Special-case compositing/copying with no scaling

When there is no scaling involved, make gdk_pixbuf_composite_color()
faster by avoiding the scaling code path.

https://bugzilla.gnome.org/show_bug.cgi?id=80927

Distrotech/gdk-pixbuf,GNOME/gdk-pixbuf,Distrotech/gdk-pixbuf,GNOME/gdk-pixbuf,GNOME/gdk-pixbuf,Distrotech/gdk-pixbuf,Distrotech/gdk-pixbuf,GNOME/gdk-pixbuf,Distrotech/gdk-pixbuf