patch 8.0.1136: W_WIDTH() is always the same

Problem:    W_WIDTH() is always the same.
Solution:   Expand the macro.
diff --git a/src/if_mzsch.c b/src/if_mzsch.c
index 6577822..c9c5969 100644
--- a/src/if_mzsch.c
+++ b/src/if_mzsch.c
@@ -2063,7 +2063,7 @@
     Vim_Prim	    *prim = (Vim_Prim *)data;
     vim_mz_window   *win = get_window_arg(prim->name, 0, argc, argv);
 
-    return scheme_make_integer(W_WIDTH(win->win));
+    return scheme_make_integer(win->win->w_width);
 }
 
 /* (set-win-width {width} [window]) */