patch 8.2.0615: regexp benchmark stest is old style

Problem:    Regexp benchmark stest is old style.
Solution:   Make it a new style test.  Fix using a NULL list.  Add more tests.
            (Yegappan Lakshmanan, closes #5963)
diff --git a/src/testdir/test_cmdline.vim b/src/testdir/test_cmdline.vim
index 8aabaa8..7d3c0c8 100644
--- a/src/testdir/test_cmdline.vim
+++ b/src/testdir/test_cmdline.vim
@@ -934,6 +934,9 @@
   let log = readfile('Xlog')
   call assert_match("foo\nbar", join(log, "\n"))
   call delete('Xlog')
+  call mkdir('Xdir')
+  call assert_fails('set verbosefile=Xdir', 'E474:')
+  call delete('Xdir', 'd')
 endfunc
 
 func Test_verbose_option()