patch 8.0.1334: splitting a window with a WinBar damages window layout

Problem:    Splitting a window with a WinBar damages window layout.
            (Lifepillar)
Solution:   Take the winbar into account when computing the new window
            position.  Add WINBAR_HEIGHT().
diff --git a/src/vim.h b/src/vim.h
index 96bab71..83ffb29 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -1485,6 +1485,11 @@
 #define MIN_COLUMNS	12	/* minimal columns for screen */
 #define MIN_LINES	2	/* minimal lines for screen */
 #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
+#else
+# define WINBAR_HEIGHT(wp)	0
+#endif
 #define QF_WINHEIGHT	10	/* default height for quickfix window */
 
 /*