libc.so.0.3 does not seem to need this defined any more.
/* We want _HURD_ITIMER_THREAD, but don't want to link in the itimer code
unnecessarily. */
-#if 0 /* libc.so.0.0 needs this defined, so make it a weak alias for now. */
extern thread_t _hurd_itimer_thread; /* XXX */
weak_extern (_hurd_itimer_thread)
-#else
-static thread_t default_hurd_itimer_thread;
-weak_alias (default_hurd_itimer_thread, _hurd_itimer_thread)
-#endif
kern_return_t
_S_msg_report_wait (mach_port_t msgport, thread_t thread,