patch 8.1.1252: not all mapping completion is tested

Problem:    Not all mapping completion is tested.
Solution:   Add a few more mapping completion tests.
diff --git a/src/testdir/test_cmdline.vim b/src/testdir/test_cmdline.vim
index f9fd80d..a822260 100644
--- a/src/testdir/test_cmdline.vim
+++ b/src/testdir/test_cmdline.vim
@@ -78,19 +78,31 @@
   call feedkeys(":map <silent> <sp\<Tab>\<Home>\"\<CR>", 'xt')
   call assert_equal('"map <silent> <special>', getreg(':'))
 
+  map <Middle>x middle
+
   map ,f commaf
   map ,g commaf
+  map <Left> left
+  map <A-Left>x shiftleft
   call feedkeys(":map ,\<Tab>\<Home>\"\<CR>", 'xt')
   call assert_equal('"map ,f', getreg(':'))
   call feedkeys(":map ,\<Tab>\<Tab>\<Home>\"\<CR>", 'xt')
   call assert_equal('"map ,g', getreg(':'))
+  call feedkeys(":map <L\<Tab>\<Home>\"\<CR>", 'xt')
+  call assert_equal('"map <Left>', getreg(':'))
+  call feedkeys(":map <A-Left>\<Tab>\<Home>\"\<CR>", 'xt')
+  call assert_equal('"map <A-Left>x', getreg(':'))
   unmap ,f
   unmap ,g
+  unmap <Left>
+  unmap <A-Left>x
 
   set cpo-=< cpo-=B 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', getreg(':'))
   unmap <Left>
 
   set cpo+=<
@@ -113,6 +125,9 @@
   call assert_equal('"map <Left>', getreg(':'))
   unmap <Left>
   set cpo-=k
+
+  unmap <Middle>x
+  set cpo&vim
 endfunc
 
 func Test_match_completion()
diff --git a/src/version.c b/src/version.c
index 13b35d5..aa0d1e6 100644
--- a/src/version.c
+++ b/src/version.c
@@ -768,6 +768,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1252,
+/**/
     1251,
 /**/
     1250,