patch 9.0.1315: escaping for completion of map command not properly tested

Problem:    Escaping for completion of map command not properly tested.
Solution:   Add a few test cases. (closes #12009)
diff --git a/src/testdir/test_cmdline.vim b/src/testdir/test_cmdline.vim
index e1c336a..ddcb260 100644
--- a/src/testdir/test_cmdline.vim
+++ b/src/testdir/test_cmdline.vim
@@ -327,17 +327,21 @@
   call assert_equal('"map <Left>', getreg(':'))
   call feedkeys(":map <A-Left>\<Tab>\<Home>\"\<CR>", 'xt')
   call assert_equal("\"map <A-Left>\<Tab>", getreg(':'))
+  call feedkeys(":map <M-Left>\<Tab>\<Home>\"\<CR>", 'xt')
+  call assert_equal("\"map <M-Left>x", getreg(':'))
   unmap ,f
   unmap ,g
   unmap <Left>
   unmap <A-Left>x
 
-  set cpo-=< cpo-=B cpo-=k
+  set cpo-=< cpo-=k
   map <Left> left
   call feedkeys(":map <L\<Tab>\<Home>\"\<CR>", 'xt')
   call assert_equal('"map <Left>', getreg(':'))
   call feedkeys(":map <M\<Tab>\<Home>\"\<CR>", 'xt')
   call assert_equal("\"map <M\<Tab>", getreg(':'))
+  call feedkeys(":map \<C-V>\<C-V><M\<Tab>\<Home>\"\<CR>", 'xt')
+  call assert_equal("\"map \<C-V><Middle>x", getreg(':'))
   unmap <Left>
 
   set cpo+=<