[scene] Add a render-internal lightid component

The vulkan shadow code needs to associate extra information with the
lights, but I don't want such renderer-specific data in the scene.

include/QF/scene/scene.h

@@ -52,6 +52,7 @@ enum scene_components {
 	scene_light,
 	scene_efrags,
 	scene_lightstyle,
+	scene_lightid,
 
 	//FIXME these should probably be private to the sw renderer (and in a
 	//group, which needs to be implemented), but need to sort out a good

libs/scene/scene.c

@@ -166,6 +166,10 @@ static const component_t scene_components[scene_comp_count] = {
 		.size = sizeof (int),
 		.name = "lightstyle",
 	},
+	[scene_lightid] = {
+		.size = sizeof (uint32_t),
+		.name = "lightid",
+	},
 
 	[scene_sw_matrix] = {
 		.size = sizeof (mat4f_t),