CHANGES:

• Breaking: peer_name (in config and epoch data, also own_name) is now a [`host] Domain_name.t instead of a string. (#434 #438 @torinnd @hannesm)
• Add a X509_async module (#435 @torinnd)
• Client and server constructor log messages are on the debug level (#436 reported by @talex5, fix by @hannesm)
• Adapt to cstruct 6.0.0 API (Cstruct.len is deprecated) #439 @hannesm