patch 8.1.0007: no test for "o" and "O" in Visual block mode

Problem:    No test for "o" and "O" in Visual block mode.
Solution:   Add a test. (Dominique Pelle, closes #2932)
diff --git a/src/testdir/test_visual.vim b/src/testdir/test_visual.vim
index 3a7d273..5b181d3 100644
--- a/src/testdir/test_visual.vim
+++ b/src/testdir/test_visual.vim
@@ -155,6 +155,25 @@
   enew!
 endfunc
 
+" Test swapping corners in blockwise visual mode with o and O
+func Test_blockwise_visual_o_O()
+  enew!
+
+  exe "norm! 10i.\<Esc>Y4P3lj\<C-V>4l2jr "
+  exe "norm! gvO\<Esc>ra"
+  exe "norm! gvO\<Esc>rb"
+  exe "norm! gvo\<C-c>rc"
+  exe "norm! gvO\<C-c>rd"
+
+  call assert_equal(['..........',
+        \            '...c   d..',
+        \            '...     ..',
+        \            '...a   b..',
+        \            '..........'], getline(1, '$'))
+
+  enew!
+endfun
+
 " Test Virtual replace mode.
 func Test_virtual_replace()
   if exists('&t_kD')