Fix compile error

[pauldeng]

Dear @tonyg,

This is a PR to fix https://github.com/tonyg/udp-exchange/issues/10.

I fixed the compile issues, now this plugin can be compiled under Erlang 26 and RabbitMQ 3.13.

However, I need your help:

• info functions seems easy
• Please help me review and fix route/3 and delete/2, I have no idea what they are

Thanks again for creating this plugin.

Cheers, Paul