we now issue a warning (at slave's server startup only) when a relay log is named
using the implicit hostname-relay-bin naming. Like we already do for binlogs.


sql/slave.cc:
  To help people avoid BUG#2122 "changing hostname confuses master or slave" until it's fixed,
  we now issue a warning (at slave's server startup only) when a relay log is named
  using the implicit hostname-relay-bin naming. Like I had already added a similar startup warning
  when a binlog is named using the implicit hostname-bin naming.
  name_warning_sent is so that at most one warning per startup is sent.