compositor-wayland: Add a --scale option

Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
diff --git a/src/compositor.c b/src/compositor.c
index 2126742..de113f1 100644
--- a/src/compositor.c
+++ b/src/compositor.c
@@ -3699,6 +3699,7 @@
 		"Options for wayland-backend.so:\n\n"
 		"  --width=WIDTH\t\tWidth of Wayland surface\n"
 		"  --height=HEIGHT\tHeight of Wayland surface\n"
+		"  --scale=SCALE\tScale factor of ouput\n"
 		"  --use-pixman\t\tUse the pixman (CPU) renderer\n"
 		"  --output-count=COUNT\tCreate multiple outputs\n"
 		"  --display=DISPLAY\tWayland display to connect to\n\n");