patch 9.0.0521: compiler warns for unused argument in small version

Problem:    Compiler warns for unused argument in small version.
Solution:   Add UNUSED.
diff --git a/src/drawline.c b/src/drawline.c
index d3eff84..07e2048 100644
--- a/src/drawline.c
+++ b/src/drawline.c
@@ -292,7 +292,7 @@
 	win_T		*wp,
 	winlinevars_T	*wlv,
 	int		sign_present UNUSED,
-	int		num_attr)
+	int		num_attr UNUSED)
 {
     if ((wp->w_p_nu || wp->w_p_rnu)
 	    && (wlv->row == wlv->startrow + wlv->filler_lines
diff --git a/src/version.c b/src/version.c
index 60c0527..36d4f99 100644
--- a/src/version.c
+++ b/src/version.c
@@ -700,6 +700,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    521,
+/**/
     520,
 /**/
     519,