Resolved merge conflict
patch for issue 456

Do not filter out duplicate subscriptions on the XSUB side of
XSUB/XPUB, so that ZMQ_XPUB_VERBOSE doesn't get blocked by forwarding
devices (as long as the devices all use ZMQ_XPUB_VERBOSE)
Code formatting
#456 was not in 3.2.2 but will be in 3.2.4
Merge pull request #85 from hintjens/master

Fix for #456 was not backported to 3.2.2; will be in 3.2.4 now