patch 8.1.1313: warnings for using localtime() and ctime()

Problem:    Warnings for using localtime() and ctime().
Solution:   Use localtime_r() if available.  Avoid using ctime().
diff --git a/src/nbdebug.c b/src/nbdebug.c
index b76d9ca..2af0288 100644
--- a/src/nbdebug.c
+++ b/src/nbdebug.c
@@ -80,12 +80,13 @@
 	char		*file;		/* possible nb_debug output file */
 	char		*cp;		/* nb_dlevel pointer */
 
-	if (log_var && (file = getenv(log_var)) != NULL) {
+	if (log_var && (file = getenv(log_var)) != NULL)
+	{
 		time_t now;
 
 		nb_debug = fopen(file, "a");
 		time(&now);
-		fprintf(nb_debug, "%s", asctime(localtime(&now)));
+		fprintf(nb_debug, "%s", get_ctime(now, TRUE));
 		if (level_var && (cp = getenv(level_var)) != NULL) {
 			nb_dlevel = strtoul(cp, NULL, 0);
 		} else {