use fhc if the rabbit application is loaded
remove unused variables
we do not need to release, fhc will take care of that
Reduce gratuitous difference from default.
Merge bug24953.
report direct connection errors as errors
add functions to unregister handlers

I have added tests for the return handler only since it is the easiest
to check. the confirm handler would be easy as well if it wasn't for
`setup_publish', which does not let you republish messages to the
exchange - I can add them if you think we need them. I would have to
set up some more code for the flow one as well.
store the `erlang:monitor/1' ref to demonitor later

Also, fix some formats
cosmetics
Merge bug25056
don't log when unregistering handles
adapter_info() -> amqp_adapter_info() in edoc
merge bug25034
simplify 'obtain' guard
fhc:obtain already masks the case when the fhc isn't running, so all
we need to do here is check that the fhc module is around.
merge bug24953 into default (again)
Merge bug25057
Unused variable warnings
trap exits in `amqp_gen_connection'
merge bug25116 into default
Mend broken links to protocol docs