patch 8.2.0577: not all modifiers supported for :options

Problem:    Not all modifiers supported for :options.
Solution:   Use all cmdmod.split flags. (closes #4401)
diff --git a/src/testdir/test_options.vim b/src/testdir/test_options.vim
index f9a424f..e03d7e9 100644
--- a/src/testdir/test_options.vim
+++ b/src/testdir/test_options.vim
@@ -87,6 +87,19 @@
   " close option-window
   close
 
+  " Open the option-window at the top.
+  set splitbelow
+  topleft options
+  call assert_equal(1, winnr())
+  close
+
+  " Open the option-window at the bottom.
+  set nosplitbelow
+  botright options
+  call assert_equal(winnr('$'), winnr())
+  close
+  set splitbelow&
+
   " Open the option-window in a new tab.
   tab options
   " Check if the option-window is opened in a tab.
@@ -94,7 +107,6 @@
   call assert_notequal('option-window', bufname(''))
   normal gt
   call assert_equal('option-window', bufname(''))
-
   " close option-window
   close