patch 9.0.0176: checking character options is duplicated and incomplete

Problem:    Checking character options is duplicated and incomplete.
Solution:   Move checking to check_chars_options(). (closes #10863)
diff --git a/src/optionstr.c b/src/optionstr.c
index 331207b..7f5a940 100644
--- a/src/optionstr.c
+++ b/src/optionstr.c
@@ -866,24 +866,8 @@
     {
 	if (check_opt_strings(p_ambw, p_ambw_values, FALSE) != OK)
 	    errmsg = e_invalid_argument;
-	else if (set_chars_option(curwin, &p_fcs, FALSE) != NULL)
-	    errmsg = e_conflicts_with_value_of_fillchars;
 	else
-	{
-	    tabpage_T	*tp;
-	    win_T	*wp;
-
-	    FOR_ALL_TAB_WINDOWS(tp, wp)
-	    {
-		if (set_chars_option(wp, &wp->w_p_lcs, FALSE) != NULL)
-		{
-		    errmsg = e_conflicts_with_value_of_listchars;
-		    goto ambw_end;
-		}
-	    }
-	}
-ambw_end:
-	{}
+	    errmsg = check_chars_options();
     }
 
     // 'background'