patch 8.2.2518: 'listchars' should be window-local

Problem:    'listchars' should be window-local.
Solution:   Make 'listchars' global-local. (Yegappan Lakshmanan, Marco Hinz,
            closes #5206, closes #7850)
diff --git a/src/testdir/test_listlbr.vim b/src/testdir/test_listlbr.vim
index 37bc44b..24bd256 100644
--- a/src/testdir/test_listlbr.vim
+++ b/src/testdir/test_listlbr.vim
@@ -43,6 +43,7 @@
 endfunc
 
 func Test_linebreak_with_list()
+  set listchars=
   call s:test_windows('setl ts=4 sbr=+ list listchars=')
   call setline(1, "\tabcdef hijklmn\tpqrstuvwxyz_1060ABCDEFGHIJKLMNOP ")
   let lines = s:screen_lines([1, 4], winwidth(0))
@@ -54,6 +55,7 @@
 \ ]
   call s:compare_lines(expect, lines)
   call s:close_windows()
+  set listchars&vim
 endfunc
 
 func Test_linebreak_with_nolist()