patch 8.2.0128: cannot list options one per line

Problem:    Cannot list options one per line.
Solution:   Use ":set!" to list one option per line.
diff --git a/src/proto/option.pro b/src/proto/option.pro
index dc07ee6..7da2cbf 100644
--- a/src/proto/option.pro
+++ b/src/proto/option.pro
@@ -8,6 +8,7 @@
 void set_init_3(void);
 void set_helplang_default(char_u *lang);
 void set_title_defaults(void);
+void ex_set(exarg_T *eap);
 int do_set(char_u *arg, int opt_flags);
 void did_set_option(int opt_idx, int opt_flags, int new_value, int value_checked);
 int string_to_key(char_u *arg, int multi_byte);