MINOR: lua: post initialisation bindings

This system permits to execute some lua function after than HAProxy
complete his initialisation. These functions are executed between
the end of the configuration parsing and check and the begin of the
scheduler.
diff --git a/include/proto/hlua.h b/include/proto/hlua.h
index 20c329b..c8d1d38 100644
--- a/include/proto/hlua.h
+++ b/include/proto/hlua.h
@@ -9,5 +9,6 @@
 int hlua_ctx_init(struct hlua *lua, struct task *task);
 void hlua_ctx_destroy(struct hlua *lua);
 void hlua_init();
+int hlua_post_init();
 
 #endif /* _PROTO_HLUA_H */