When a client with an in-use client-id connects, if the old client has a
will, send the will message. Closes #26.

Thanks to Pierre F.

These are no longer supported by openssl.

Closes #567 and #715.

This allows a second connect callback to be used that exposes the
MQTT connect flags parameter.

Closes #738, #128.

Closes #776.

Closes #724.

Thanks to Hrvoje Šeketa.

_mosquitto_net_read must call WSASetLastError when changing errno so that the error code can be picked up by _mosquitto_packet_read

Signed-off-by: Thomas Beckmann (M-Way) <t.beckmann@mwaysolutions.com>

Signed-off-by: Tifaifai Maupiti <tifaifai.maupiti@gmail.com>

Closes: #765.