patch 9.1.1391: Vim does not have a vertical tabpanel

Problem:  Vim does not have a tabpanel
Solution: include the tabpanel feature
          (Naruhiko Nishino, thinca)

closes: #17263

Co-authored-by: thinca <thinca@gmail.com>
Signed-off-by: Naruhiko Nishino <naru123456789@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/proto/tabpanel.pro b/src/proto/tabpanel.pro
new file mode 100644
index 0000000..3cbaa2f
--- /dev/null
+++ b/src/proto/tabpanel.pro
@@ -0,0 +1,7 @@
+/* tabpanel.c */
+int tabpanel_width(void);
+int tabpanel_leftcol(win_T	*wp);
+int tabpanelopt_changed(void);
+void draw_tabpanel(void);
+int get_tabpagenr_on_tabpanel(void);
+/* vim: set ft=c : */