patch 8.0.0483: illegal memory access when using :all

Problem:    Illegal memory access when using :all. (Dominique Pelle)
Solution:   Adjust the cursor position right after setting "curwin".
diff --git a/src/testdir/test_window_cmd.vim b/src/testdir/test_window_cmd.vim
index 569a78a..6c9ddc2 100644
--- a/src/testdir/test_window_cmd.vim
+++ b/src/testdir/test_window_cmd.vim
@@ -67,4 +67,16 @@
   augroup! test_window_cmd_wincmd_gf
 endfunc
 
+func Test_next_split_all()
+  " This was causing an illegal memory access.
+  n x
+  norm axxx
+  split
+  split
+  s/x
+  s/x
+  all
+  bwipe!
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab