Improve performance of the proxy forwarding batch of message.
Add throughput benchmark for proxy.
Fix valgrind error reported on unitialized vars
RELICENSE: Add emtr grant

This reverts commit ac19d5f4.

Solution: add test case run with cap_net_admin
Fixes #3397

Solution: define UNITY_SUPPORT_64 to force 64 bit support

Solution: move general monitoring test utilities to new testutil_monitoring

Solution: migrate to unity

Solution: add monitor event socket option

Solution: extract common base class stream_listener_base_t

Solution: extract common base class stream_connecter_base_t

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: mark it as XFAIL like the other tests that use ipc://*

Solution: migrate to unity

Solution: migrate to unity

Solution: use the same for both autotools and cmake

Solution: go back to using -Wl,--version-script.

Use ax_check_vscript.m4 from the autoconf-archive to detect support on
multiple platforms (eg Solaris ld(1) -M).

libtool -export-symbols-regexp used ld(1) --retain-symbols-file under
the hood, the latter lets some C++ weak symbols make their way into the
dynamic symbols table, along with the zmq_* interface.  The reason for
such behavior is unknown to me.

Solution: migrate to unity

Solution: migrate to unity

Solution: the generic approach taken in 70b48a9c allows us to use the
same LDFLAGS on most platforms.

Solution: delete it

Solution: switch to libtool symbol visibility support, which leads to
more portable constructs in the autotools glue.  As noted in the libtool
documentation "This option has no effect on some platforms."

After this commit, global symbols intended to be kept private will
disappear on platforms that were previously not handled
using -Wl,--version-script.

Solution: remove stray -Wl.

* Problem: radix tree needs benchmarks and improvements

Solution: add a benchmark and make suggested improvements

Solution: skip tests that use ipc://* as it's impossible to get the
address back for the client

Solution: use a different system variable for debian/hurd and
debian/kfreebsd so that the tests are skipped only on hurd.

subscriptions increases

Solution: use a radix tree instead of a trie to store subscriptions

Solution: use a monitor to wait for a disconnect instead of a sleep,
and retry to send a message until it fails since the state machine
might be delayed due to the I/O thread being pre-empted on busy
systems.
Also set a receive timeout to avoid random hangs.

Fixes #3124

Add new HWM tests and more detailed documentation

This reverts commit fd27324e.

Solution: migrate to unity

Solution: merge into a single test_use_fd and reduce code duplication by extracting common functions

Solution: migrate to unity

Solution: migrate to unity

Solution: migrate to unity

Solution: migrate to unity

Solution: migrate to unity

Solution: migrate to unity

Solution: migrate to unity

Solution: migrate to unity

Solution: migrate to unity

Solution: migrate to unity