Solution: add initial version of documentation

Solution: mark test_rebind_ipc as XFAIL on Hurd as it does not
implement getsockname on IPC and thus it's impossible to use
wildcard IPC binds.
Document that ZMQ_LAST_ENDPOINT does not work on Hurd with IPC.

Solution: remove documents and tests for ZMQ_THREAD_PRIORITY getter. It
never worked and can never work as it has the same value as a get-only
option ZMQ_SOCKET_LIMIT. It cannot be changed without breaking ABI.
Note that the setter works fine as ZMQ_SOCKET_LIMIT is get-only.

Noticed there was a small typo in the documentation.

Solution: add it

Solution: add one so that class-based bindings can easily use them

Solution: do it

Solution: Add more information to the doc specifying that MAX_INT is the maximum
possible return value.

Add new HWM tests and more detailed documentation

* Add ZMQ_ROUTER_NOTIFY draft socket option

Solution: add it to the makefile

Solution: add a manpage
Fixes #3005

* More info on conflate queue

* update pair doc

Solution: use UINT16_MAX

* Update zmq_connect documentation to mention issue of multiple connects to the same endpoint

Solution: add symlinks to zmq_poller.txt

Solution: add initial documentation

Solution: update to document new binding options and IPv6 support

Solution: add a new ZMQ_MULTICAST_LOOP option for UDP sockets.

Solution: mention in manpage that if the timeout is not set and the
interval is, the timeout will be equal to the interval

Solution: add note like for radio-dish
Fixes: #3050

Solution: revert the revert!

Revert "Problem: regression in 4.2.3 went unnoticed, want to release 4.2.5"

This reverts commit 5f17e26f.

Solution: revert DRAFT -> STABLE API transition so that we can do a
bugfix-only 4.2.5 release.
Will be re-reverted once tagged.

Revert "Problem: ZMQ_BINDTODEVICE has met STABLE conditions"

This reverts commit 3cb79f50.

Revert "Problem: ZMQ_MSG_GSSAPI_* have met STABLE conditions"

This reverts commit 374da420.

Revert "Problem: ZMQ_MSG_T_SIZE has met STABLE conditions"

This reverts commit 6411c4a2.

Revert "Problem: docs say STABLE API still in DRAFT"

This reverts commit 9f2f30b7.

Solution: fix it, as since 4.2.0 there is no ordering constraint
anymore
Fixes: #2854

Solution: clarify it since it's a common source of confusion

Solution: update them

Solution: update manpages

Solution: move it from DRAFT to STABLE since it's been in a public
release, committed for 6+ months and has not changed.
Given a new STABLE symbol has been added, bump minor version number.

The zero copy decoding strategy implemented for 4.2.0 can lead to a large
increase of main memory usage in some cases (I have seen one program go up to
40G from 10G after upgrading from 4.1.4). This commit adds a new option to
contexts, called ZMQ_ZERO_COPY_RECV, which allows one to switch to the old
decoding strategy.

Solultion: clarify that notifications for unique subs/unsubs are always
passed, and these option only affect the behaviour for duplicated ones.

Problem: Wrong linger default value

Solution: correct documentation

Solution: add them

Change ZMQ_THREAD_AFFINITY to ZMQ_THREAD_AFFINITY_CPU_ADD/ZMQ_THREAD_AFFINITY_CPU_REMOVE. Avoid prefix thread names when no prefix was set.

Solution: provide correct description

Fixes #2789

* Clarify usage of zmq_close

Solution: mention that the STATISTICS command returns a message with 8
frames