And I'm on a reasonably sized laptop. I think allocating INT_MAX
memory is dangerous in a test case.

Solution: expose this as a context option. I've used ZMQ_MAX_MSGSZ
and documented it and implemented the API. However I don't know how
to get the parent context for a socket, so the code in zmq.cpp is
still unfinished.

These options are confusing and redundant. Their names suggest
they apply to the tcp:// transport, yet they are used for all
stream protocols. The methods zmq::set_tcp_receive_buffer and
zmq::set_tcp_send_buffer don't use these values at all, they use
ZMQ_SNDBUF and ZMQ_RCVBUF.

Solution: merge these new options into ZMQ_SNDBUF and ZMQ_RCVBUF.

This means defaulting these two options to 8192, and removing the
new options. We now have ZMQ_SNDBUF and ZMQ_RCVBUF being used both
for TCP socket control, and for input/output buffering.

Note: the default for SNDBUF and RCVBUF are otherwise 4096.

The proper name is ZMQ_THREAD_SAFE

Solution: fix in the documentation.

This option has a few issues. The name is long and clumsy. The
functonality is not smooth: one must set both this and
ZMQ_XPUB_VERBOSE at the same time, or things will break mysteriously.

Solution: rename to ZMQ_XPUB_VERBOSER and make an atomic option.

That is, implicitly does ZMQ_XPUB_VERBOSE.

Solution: rename to ZMQ_MAXRT

This is the option name used on Windows, so easier to use and
remember.

Solution: rename socket option (and variables and files) from usefd
to use_fd.

Solution: rename socket option (and variables and files) from
pre_allocated_fd to usefd.

Solution: be more explicit in the code, and in the zmq_recv man
page (which is the most unobvious case). Assert if length is not
zero and buffer is nonetheless null.

Solution: add new [set|get]sockopt ZMQ_PRE_ALLOCATED_FD to allow
users to let ZMQ use a pre-allocated file descriptor instead of
allocating a new one. Update [set|get]sockopt documentation and
test accordingly.

The main use case for this feature is a socket-activated systemd
service. For more information about this feature see:
http://0pointer.de/blog/projects/socket-activation.html

Solution: Replace with `zmq_ctx_term`

These sockets don't handle multipart data, so if callers send it,
they drop frames, and things break silently.

Solution: if the caller tries to use ZMQ_SNDMORE, return -1 and
set errno to EINVAL.

Solution: fix this.

VMCI transport allows fast communication between the Host
and a virtual machine, between virtual machines on the same host,
and within a virtual machine (like IPC).

It requires VMware to be installed on the host and Guest Additions
to be installed on a guest.

Fixes #1646

Solution: fix documentation

Solution: change option behaviour and adopt documentation

Without this change, a segmentation fault is likely to occur when using the proposed snippet of code, as `*address[size]` is equivalent to `*(address[size])`, not `(*address)[size]` as clearly intended.

- both are thread safe
- they do not accept ZMQ_SNDMORE nor ZMQ_RCVMORE

REQ-REP barely work, and DEALER-ROUTER are misnamed. As we move to
formalizing CLIENT-SERVER, we can deprecate request-reply.

Solution: move this section to the end of the man page, and mark as
"will be deprecated".

Solution: add man pages/sections for:

 * ZMQ_SERVER
 * ZMQ_CLIENT
 * ZMQ_THREADSAFE
 * zmq_msg_routing_id
 * zmq_msg_set_routing_id

The order of zmq_bind() and zmq_connect() is no longer important
for the inproc transport since libzmq 4.0.  This updates this
in the zmq_inproc manpage.

Solution: fix it. Default is true, not false.

was fixed in zmq_setsockopt.txt but not in zmq_getsockopt.txt

Fixes not receiving unsubscription messages in XPUB socket with
ZMQ_XPUB_VERBOSE and using a XSUB-XPUB proxy in front.

This adds two modifications:

- It adds a new flag, ZMQ_XPUB_VERBOSE_UNSUBSCRIBE, to enable verbose
  unsubscription messages, necessary when using a XSUB/XPUB proxy.

- It adds a boolean switch to zmq::mtrie_t::rm () to control if the
  callback is invoked every time or only in the last removal. Necessary
  when a pipe is terminated and the verbose mode for unsubscriptions is
  enabled.

Added documentation about context's options ZMQ_THREAD_SCHED_POLICY and ZMQ_THREAD_PRIORITY