Get at the length field of sha-512
Get at the length field of sha-512

This lets us take the hash of old-world strings with a bunch of trailing
zero bytes.

jfranklin9000/urbit,ngzax/urbit,cgyarvin/urbit-1,jfranklin9000/urbit,max19/urbit,max19/urbit,juped/your-urbit,juped/your-urbit,ngzax/urbit,jfranklin9000/urbit,cgyarvin/urbit-1,ngzax/urbit,urbit/urbit,ohAitch/urbit,max19/urbit,jfranklin9000/urbit,ohAitch/urbit,max19/urbit,urbit/urbit,cgyarvin/urbit-1,max19/urbit,cgyarvin/urbit-1,juped/your-urbit,juped/your-urbit,juped/your-urbit,juped/your-urbit,juped/your-urbit,ngzax/urbit,urbit/urbit,ohAitch/urbit,juped/urbit,jfranklin9000/urbit,ngzax/urbit,max19/urbit,ohAitch/urbit,ngzax/urbit,ngzax/urbit,juped/your-urbit,urbit/urbit,ohAitch/urbit,cgyarvin/urbit-1,juped/urbit,cgyarvin/urbit-1,juped/your-urbit,juped/urbit,ohAitch/urbit,juped/urbit,ohAitch/urbit,ohAitch/urbit,cgyarvin/urbit-1,urbit/urbit,juped/urbit,max19/urbit,ohAitch/urbit,juped/your-urbit,ohAitch/urbit,urbit/urbit,max19/urbit,cgyarvin/urbit-1,juped/urbit,juped/urbit,jfranklin9000/urbit,urbit/urbit,juped/urbit,jfranklin9000/urbit