Closes #804.

Thanks to Nicola Lunghi.

Closes #533493 (on Eclipse bugtracker)

Thanks to Daniel Romero.

Closes #704
Closes #705
Closes #730
Closes #732

Thanks to Umberto Boscolo.

Signed-off-by: Eric Schneeberger <eric.schneeberger@gtt.com>

_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>

Don't allow username when no username flag set.
Don't allow password when no password flag set.

Closes #730. Closes #731.

Thanks to Umberto Boscolo.

Closes #693.

This limits the use of those options to openssl 1.1.0 and greater.