patch 8.2.0656: MS-Windows: redrawing right screen edge may not be needed

Problem:    MS-Windows: redrawing right screen edge may not be needed.
Solution:   Check the build version. (Nobuhiro Takasaki, closes #6002)
diff --git a/src/proto/os_win32.pro b/src/proto/os_win32.pro
index e60ce92..15c1323 100644
--- a/src/proto/os_win32.pro
+++ b/src/proto/os_win32.pro
@@ -79,5 +79,6 @@
 int has_conpty_working(void);
 int get_conpty_type(void);
 int is_conpty_stable(void);
+int get_conpty_fix_type(void);
 void resize_console_buf(void);
 /* vim: set ft=c : */