Minimal additional fixes for with both clang16 and older clang.

https://bugs.gentoo.org/870631
See also: https://github.com/phokz/pwauth/pull/13
--- a/auth_sun.c
+++ b/auth_sun.c
@@ -33,2 +33,3 @@
 
+#include <time.h>
 #include "pwauth.h"
--- a/fail_log.c
+++ b/fail_log.c
@@ -33,2 +33,3 @@
 
+#include <time.h>
 #include "pwauth.h"
@@ -72,3 +73,3 @@
 
-void log_failure()
+void log_failure(void)
 {
@@ -151,3 +152,3 @@
 
-log_failure()
+void log_failure(void)
 {
--- a/nologin.c
+++ b/nologin.c
@@ -40,3 +40,3 @@
 
-check_nologin()
+int check_nologin(void)
 {
--- a/pwauth.h
+++ b/pwauth.h
@@ -133 +133,3 @@
 int check_auth(char *login, char *passwd);
+int check_nologin(void);
+void log_failure(void);