patch 8.1.1840: Testing: WorkingClipboard() is not accurate

Problem:    Testing: WorkingClipboard() is not accurate.
Solution:   Check feature clipboard_working instead.
diff --git a/src/testdir/shared.vim b/src/testdir/shared.vim
index 54a37f3..a4a7179 100644
--- a/src/testdir/shared.vim
+++ b/src/testdir/shared.vim
@@ -322,13 +322,3 @@
   endif
   return 1
 endfunc
-
-func WorkingClipboard()
-  if !has('clipboard')
-    return 0
-  endif
-  if has('x11')
-    return $DISPLAY != ""
-  endif
-  return 1
-endfunc
diff --git a/src/testdir/test_paste.vim b/src/testdir/test_paste.vim
index eab4cff..c30140f 100644
--- a/src/testdir/test_paste.vim
+++ b/src/testdir/test_paste.vim
@@ -70,9 +70,8 @@
 endfunc
 
 func Test_paste_clipboard()
-  if !WorkingClipboard()
-    return
-  endif
+  CheckFeature clipboard_working
+
   let @+ = "nasty\<Esc>:!ls\<CR>command"
   new
   exe "normal i\<C-R>+\<Esc>"
diff --git a/src/testdir/test_quotestar.vim b/src/testdir/test_quotestar.vim
index d21ab35..432862e 100644
--- a/src/testdir/test_quotestar.vim
+++ b/src/testdir/test_quotestar.vim
@@ -1,11 +1,9 @@
 " *-register (quotestar) tests
 
 source shared.vim
-if !WorkingClipboard()
-  throw 'Skipped: no working clipboard'
-endif
+source check.vim
 
-source shared.vim
+CheckFeature clipboard_working
 
 func Do_test_quotestar_for_macunix()
   if empty(exepath('pbcopy')) || empty(exepath('pbpaste'))
diff --git a/src/testdir/test_termcodes.vim b/src/testdir/test_termcodes.vim
index 475a09a..75eaa7b 100644
--- a/src/testdir/test_termcodes.vim
+++ b/src/testdir/test_termcodes.vim
@@ -182,9 +182,7 @@
 endfunc
 
 func Test_term_mouse_middle_click()
-  if !WorkingClipboard()
-    throw 'Skipped: No working clipboard'
-  endif
+  CheckFeature clipboard_working
 
   new
   let save_mouse = &mouse
diff --git a/src/version.c b/src/version.c
index aa44fb0..8e79926 100644
--- a/src/version.c
+++ b/src/version.c
@@ -770,6 +770,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1840,
+/**/
     1839,
 /**/
     1838,