patch 8.1.0864: cannot have a local value for 'scrolloff' and 'sidescrolloff'

Problem:    Cannot have a local value for 'scrolloff' and 'sidescrolloff'.
            (Gary Holloway)
Solution:   Make 'scrolloff' and 'sidescrolloff' global-local. (mostly by
            Aron Widforss, closes #3539)
diff --git a/src/window.c b/src/window.c
index d89f3a8..f78fcca 100644
--- a/src/window.c
+++ b/src/window.c
@@ -4594,6 +4594,10 @@
     new_wp->w_cursor.lnum = 1;
     new_wp->w_scbind_pos = 1;
 
+    // use global option value for global-local options
+    new_wp->w_p_so = -1;
+    new_wp->w_p_siso = -1;
+
     /* We won't calculate w_fraction until resizing the window */
     new_wp->w_fraction = 0;
     new_wp->w_prev_fraction_row = -1;
@@ -5871,7 +5875,7 @@
 
     if (wp == curwin)
     {
-	if (p_so)
+	if (get_scrolloff_value())
 	    update_topline();
 	curs_columns(FALSE);	/* validate w_wrow */
     }