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/evalfunc.c b/src/evalfunc.c
index 6c2a73e..7b019a5 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -13239,7 +13239,7 @@
 
 	check_cursor();
 	win_new_height(curwin, curwin->w_height);
-	win_new_width(curwin, W_WIDTH(curwin));
+	win_new_width(curwin, curwin->w_width);
 	changed_window_setting();
 
 	if (curwin->w_topline <= 0)