vim-patch:8.2.3424: a sequence of spaces is hard to see in list mode

Problem:    A sequence of spaces is hard to see in list mode.
Solution:   Add the "multispace" option to 'listchars'. (closes vim/vim#8834)
f14b8ba137

src/nvim/buffer_defs.h

@@ -1214,6 +1214,7 @@ struct window_S {
     int tab3;                       ///< third tab character
     int lead;
     int trail;
+    int *multispace;
     int conceal;
   } w_p_lcs_chars;