patch 8.2.0848: MS-Windows: the Windows terminal code has some flaws

Problem:    MS-Windows: the Windows terminal code has some flaws.
Solution:   Do not redraw the right edge of the screen.  Remove the background
            color trick.  Flush the screen output buffer often.  (Nobuhiro
            Takasaki, #5546)
diff --git a/src/proto/os_win32.pro b/src/proto/os_win32.pro
index d8f9ac3..85c09c0 100644
--- a/src/proto/os_win32.pro
+++ b/src/proto/os_win32.pro
@@ -71,6 +71,8 @@
 void set_alist_count(void);
 void fix_arg_enc(void);
 int mch_setenv(char *var, char *value, int x);
+int vtp_printf(char *format, ...);
+int use_wt(void);
 void get_default_console_color(int *cterm_fg, int *cterm_bg, guicolor_T *gui_fg, guicolor_T *gui_bg);
 void control_console_color_rgb(void);
 int use_vtp(void);