This is needed for openssl 1.1. Sadly this breaks json_fwd.hpp
detection, so it was removed (for now at least).

Adds function to set presence explicitly, query presence explicitly and
to set presence explicitly on sync as well as receive presence updates.

Hunter wants you to set the standard via a toolchain file, but some
distros may override that. See #30.

Rename RelatesTo for reply messages

The bug fix for the race condition on handler execution used the new
strand interface. While it is possible to use bind_executor on every
call, that is error prone and not the suggested usage anymore.