[gl,glsl,sw] Skip onlyshadows alias models

While the gl renderer does (or did) have it's attempt at shadows, the
others don't even try, thus the onlyshadows-marked player model doesn't
work so well (looks rather goofy seeing the arms like that).

libs/video/renderer/gl/gl_mod_alias.c

@@ -415,6 +415,10 @@ gl_R_DrawAliasModel (entity_t e)
 	renderer_t *renderer = Ent_GetComponent (e.id, scene_renderer, e.reg);
 	model_t    *model = renderer->model;
 
+	if (renderer->onlyshadows) {
+		return;
+	}
+
 	radius = model->radius;
 	transform_t transform = Entity_Transform (e);
 	origin = Transform_GetWorldPosition (transform);

libs/video/renderer/glsl/glsl_alias.c

@@ -242,6 +242,9 @@ glsl_R_DrawAlias (entity_t ent)
 	calc_lighting (ent, &ambient, &shadelight, lightvec);
 
 	renderer_t *renderer = Ent_GetComponent (ent.id, scene_renderer, ent.reg);
+	if (renderer->onlyshadows) {
+		return;
+	}
 	model_t    *model = renderer->model;
 	if (!(hdr = model->aliashdr))
 		hdr = Cache_Get (&model->cache);

libs/video/renderer/sw/sw_ralias.c

@@ -617,6 +617,9 @@ R_AliasDrawModel (entity_t ent, alight_t *lighting)
 	r_amodels_drawn++;
 
 	renderer_t *renderer = Ent_GetComponent (ent.id, scene_renderer, ent.reg);
+	if (renderer->onlyshadows) {
+		return;
+	}
 	if (!(paliashdr = renderer->model->aliashdr))
 		paliashdr = Cache_Get (&renderer->model->cache);
 	pmdl = (mdl_t *) ((byte *) paliashdr + paliashdr->model);