This can be used by plugins to determine which version of MQTT a client
has connected with.

Closes #1735. Thanks to Brian Orpin.

Add a refcount around mosquitto_lib_init and mosquitto_lib_cleanup so
that multiple calls to init/cleanup don't trigger memory leaks or
double-frees.

Signed-off-by: Martin Kelly <mkelly@xevo.com>

Signed-off-by: Abilio Marques <abiliojr@gmail.com>

Merge branch 'rfc-bridge-local-clean' of git://github.com/etactica/mosquitto into etactica-rfc-bridge-local-clean

This applies if connecting to a v3.x only broker.

Issue #1641.

All strings are already validated in packet__read_string().

This adds the ability to separating bridge clean session settings between
the local and remote endpoints.  Some broker implmentations refuse to allow
non-clean sessions, as they don't support storing messages to be sent to
the connecting broker.  However, this doesn't mean that the local
broker can't be queueing messages to send _out_ to the remote broker.

This PR adds a new bridge connection setting, local_cleansession, that
allows controlling this split. Naming is chosen to be local_ in keeping
with the other local_ settings for bridges.

A test for the six cases of queued/not queued messages in both
directions is added, but v5 testing is currently disabled.  The changes
to support the split are ~independent of protocol version.

Signed-off-by: Karl Palsson <karlp@etactica.com>

Like do_send_receive() but aimed for mocking the other side.

Signed-off-by: Karl Palsson <karlp@etactica.com>