patch 8.1.1587: redraw problem when sign icons in the number column

Problem:    Redraw problem when sign icons in the number column.
Solution:   Clear and redraw when changing related options.  Right aligh the
            sign icon in the GUI. (Yegappan Lakshmanan, closes #4578)
diff --git a/src/gui.c b/src/gui.c
index 5689182..634f3fb 100644
--- a/src/gui.c
+++ b/src/gui.c
@@ -2253,6 +2253,7 @@
     int		col = gui.col;
 #ifdef FEAT_SIGN_ICONS
     int		draw_sign = FALSE;
+    int		signcol = 0;
     char_u	extra[18];
 # ifdef FEAT_NETBEANS_INTG
     int		multi_sign = FALSE;
@@ -2287,6 +2288,8 @@
 	if (len == 1 && col > 0)
 	    --col;
 	len = (int)STRLEN(s);
+	if (len > 2)
+	    signcol = len - 3;	// Right align sign icon in the number column
 	draw_sign = TRUE;
 	highlight_mask = 0;
     }
@@ -2612,7 +2615,7 @@
 #ifdef FEAT_SIGN_ICONS
     if (draw_sign)
 	/* Draw the sign on top of the spaces. */
-	gui_mch_drawsign(gui.row, col, gui.highlight_mask);
+	gui_mch_drawsign(gui.row, signcol, gui.highlight_mask);
 # if defined(FEAT_NETBEANS_INTG) && (defined(FEAT_GUI_X11) \
 	|| defined(FEAT_GUI_GTK) || defined(FEAT_GUI_MSWIN))
     if (multi_sign)