Enable Scroll Lock LED to be used as Compose LED
With this patch, the "Use keyboard LED to indicate modifiers / Compose" setting (within Key Bindings) causes the Scroll Lock LED to be used as a Compose LED. (I.e., the LED will illuminate when one is in the middle of a compose sequence.)
Without this patch, the setting has no effect, because modern keyboards don't have Compose LEDs. The best explanation that I could find of what this setting is supposed to do is here.