Avoid backwards clock in movemail timestamps

* lib-src/movemail.c (mbx_delimit_begin): Use ‘current_timespec’
instead of ‘time’ to generate the user-visible timestamp.
This works around the minor glitch caused by glibc bug 30200
<https://sourceware.org/bugzilla/show_bug.cgi?id=30200>.

lib-src/movemail.c

@@ -846,7 +846,7 @@ movemail_strftime (char *s, size_t size, char const *format,
 static bool
 mbx_delimit_begin (FILE *mbf)
 {
-  time_t now = time (NULL);
+  time_t now = current_timespec ().tv_sec;
   struct tm *ltime = localtime (&now);
   if (!ltime)
     return false;