patch 8.0.1375: window size wrong after maximizing with WinBar

Problem:    Window size wrong after maximizing with WinBar. (Lifepillar)
Solution:   Fix height computations. Redraw window when it is zero height but
            has a WinBar. (closes #2356)
diff --git a/src/vim.h b/src/vim.h
index bf6c3d3..b43c210 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -1478,8 +1478,10 @@
 #define STATUS_HEIGHT	1	/* height of a status line under a window */
 #ifdef FEAT_MENU		/* height of a status line under a window */
 # define WINBAR_HEIGHT(wp)	(wp)->w_winbar_height
+# define VISIBLE_HEIGHT(wp)	((wp)->w_height + (wp)->w_winbar_height)
 #else
 # define WINBAR_HEIGHT(wp)	0
+# define VISIBLE_HEIGHT(wp)	(wp)->w_height
 #endif
 #define QF_WINHEIGHT	10	/* default height for quickfix window */