Fix uninitialized nstime reading / updating on the stack in hpa.

In order for nstime_update to handle non-monotonic clocks, it requires the input
nstime to be initialized -- when reading for the first time, zero init has to be
done.  Otherwise random stack value may be seen as clocks and returned.

include/jemalloc/internal/hpa_hooks.h

@@ -8,7 +8,7 @@ struct hpa_hooks_s {
 	void (*purge)(void *ptr, size_t size);
 	void (*hugify)(void *ptr, size_t size);
 	void (*dehugify)(void *ptr, size_t size);
-	void (*curtime)(nstime_t *r_time);
+	void (*curtime)(nstime_t *r_time, bool first_reading);
 };
 
 extern hpa_hooks_t hpa_hooks_default;