Defining static data in the header causes warnings on Apple gcc, and in general
this should be the client's responsibility. The names are obvious from the
log_level enum, which is public, and it's only one line of boilerplate to
copy in implementing a custom logging function.
now derives the domain from the jid.
Is it reasonable to just remove the 'domain' (more properly server) argument directly?
The library should always handle this and I can't think why you'd want to override unless
maybe if you have a proxy.