patch 8.2.1780: statusline not updated when splitting windows

Problem:    Statusline not updated when splitting windows.
Solution:   Call status_redraw_all(). (Jason Franklin, closes #5496)
diff --git a/src/testdir/test_statusline.vim b/src/testdir/test_statusline.vim
index f73998a..d8e921f 100644
--- a/src/testdir/test_statusline.vim
+++ b/src/testdir/test_statusline.vim
@@ -433,4 +433,21 @@
   call delete('XTest_statusline')
 endfunc
 
+func Test_statusline_after_split_vsplit()
+  only
+
+  " Make the status line of each window show the window number.
+  set ls=2 stl=%{winnr()}
+
+  split | redraw
+  vsplit | redraw
+
+  " The status line of the third window should read '3' here.
+  call assert_equal('3', nr2char(screenchar(&lines - 1, 1)))
+
+  only
+  set ls& stl&
+endfunc
+
+
 " vim: shiftwidth=2 sts=2 expandtab