patch 8.2.1228: scrollbars not flush against the window edges when maximised

Problem:    Scrollbars not flush against the window edges when maximised.
Solution:   Add padding. (Ken Takata, closes #5602, closes #6466)
diff --git a/src/proto/gui_w32.pro b/src/proto/gui_w32.pro
index 4ead92e..68e45b3 100644
--- a/src/proto/gui_w32.pro
+++ b/src/proto/gui_w32.pro
@@ -14,6 +14,8 @@
 void gui_mch_set_text_area_pos(int x, int y, int w, int h);
 void gui_mch_enable_scrollbar(scrollbar_T *sb, int flag);
 void gui_mch_set_scrollbar_pos(scrollbar_T *sb, int x, int y, int w, int h);
+int gui_mch_get_scrollbar_xpadding(void);
+int gui_mch_get_scrollbar_ypadding(void);
 void gui_mch_create_scrollbar(scrollbar_T *sb, int orient);
 int gui_mch_adjust_charheight(void);
 GuiFont gui_mch_get_font(char_u *name, int giveErrorIfMissing);