tls: init tls hooks to {0}, avoiding fields enumeration

- if a new field is added, then should be no longer needed to update
  initialization

tls_hooks.c

@@ -28,7 +28,7 @@
 
 #ifdef TLS_HOOKS
 
-struct tls_hooks tls_hook= {0,0,0,0,0,0,0,0};
+struct tls_hooks tls_hook= {0};
 
 static int tls_hooks_loaded=0;