patch 8.2.4317: MS-Windows: Vim exits when Python 3 initialisation fails

Problem:    MS-Windows: Vim exits when Python 3 initialisation fails.
Solution:   Hook into the exit() function to recover from the failure.
            (Ken Takata, closes #9710)
diff --git a/src/proto/os_win32.pro b/src/proto/os_win32.pro
index 5c50816..dac2b71 100644
--- a/src/proto/os_win32.pro
+++ b/src/proto/os_win32.pro
@@ -3,6 +3,7 @@
 int mch_is_gui_executable(void);
 HINSTANCE find_imported_module_by_funcname(HINSTANCE hInst, const char *funcname);
 void *get_dll_import_func(HINSTANCE hInst, const char *funcname);
+void *hook_dll_import_func(HINSTANCE hInst, const char *funcname, const void *hook);
 int dyn_libintl_init(void);
 void dyn_libintl_end(void);
 void PlatformId(void);