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/evalfunc.c b/src/evalfunc.c
index b3da9f6..bee76c6 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -9736,7 +9736,8 @@
 	    {
 		cchar = syn_get_sub_char();
 		if (cchar == NUL && curwin->w_p_cole == 1)
-		    cchar = (lcs_conceal == NUL) ? ' ' : lcs_conceal;
+		    cchar = (curwin->w_lcs_chars.conceal == NUL) ? ' '
+					: curwin->w_lcs_chars.conceal;
 		if (cchar != NUL)
 		{
 		    if (has_mbyte)