patch 9.0.0571: MS-Windows: CTRL-C can make Vim exit

Problem:    MS-Windows: CTRL-C can make Vim exit.
Solution:   Check the not-a-term argument.
diff --git a/src/proto/main.pro b/src/proto/main.pro
index 4368e24..f0f9b73 100644
--- a/src/proto/main.pro
+++ b/src/proto/main.pro
@@ -2,6 +2,7 @@
 int vim_main2(void);
 void common_init(mparm_T *paramp);
 int is_not_a_term(void);
+int is_not_a_term_or_gui(void);
 char_u *get_gui_dialog_file(void);
 int op_pending(void);
 void may_trigger_safestate(int safe);