Add localtime_r() declaration in case it isn't available

configure.ac

@@ -358,6 +358,7 @@ AC_SUBST(PSL_TESTFILE)
 
 AC_CHECK_FUNCS([strdup strndup clock_gettime fmemopen nl_langinfo])
 AC_CHECK_DECLS([strdup])
+AC_CHECK_DECLS([localtime_r])
 
 # check for dirent.h
 AC_HEADER_DIRENT

tools/psl.c

@@ -41,11 +41,15 @@
 
 // Windows does not have localtime_r but has localtime_s, which is more or less
 // the same except that the arguments are reversed
-# define LOCALTIME_R_SUCCESSFUL(t_sec,t_now)	\
+# define LOCALTIME_R_SUCCESSFUL(t_sec, t_now)	\
 	(localtime_s(t_now, t_sec) == 0)
 #else
 # include <time.h>
-# define LOCALTIME_R_SUCCESSFUL(t_sec,t_now)	\
+# if ! HAVE_DECL_LOCALTIME_R
+struct tm *localtime_r(const time_t *, struct tm *);
+#endif
+
+# define LOCALTIME_R_SUCCESSFUL(t_sec, t_now)	\
 	(localtime_r(t_sec, t_now) != NULL)
 #endif