patch 8.0.1138: click in window toolbar starts Visual mode

Problem:    Click in window toolbar starts Visual mode.
Solution:   Add the MOUSE_WINBAR flag.
diff --git a/src/normal.c b/src/normal.c
index d2d1a29..d78a53b 100644
--- a/src/normal.c
+++ b/src/normal.c
@@ -2794,6 +2794,12 @@
      */
     jump_flags = jump_to_mouse(jump_flags,
 			oap == NULL ? NULL : &(oap->inclusive), which_button);
+
+#ifdef FEAT_MENU
+    /* A click in the window toolbar has no side effects. */
+    if (jump_flags & MOUSE_WINBAR)
+	return FALSE;
+#endif
     moved = (jump_flags & CURSOR_MOVED);
     in_status_line = (jump_flags & IN_STATUS_LINE);
     in_sep_line = (jump_flags & IN_SEP_LINE);