autogen.sh has a check for the libtool binary as a mean to
check if libtool is available. But distributions like Debian and
Ubuntu are splitting the libtool package, and the libtool binary is now
in a separate package. What autoconf actually need is not the libtool
binary, but libtoolize and other macro files. So check for libtoolize
instead. On the other hand, OSX only ships libtool, not libtoolize,
and uses a pre-generated libtool script to build. So check for
libtoolize first and then for libtool, and fail if neither can be
found.

Add a way to disable libzmq's internal test timeout.

Increase sleep in test to fix flakiness under CPU load.

Retry recv if it only returns part of a message during tests.

Fix test flakiness.

Fix a documented memory leak.

Fix eventfd read handling under heavy load.

Under linux 3.16.0-4-amd64, I was getting occasional test failures
before fixing this.

I had the assertion below fail occasionally when running the libzmq
tests under heavy CPU load on linux 3.16.0-4-amd64.

I'm pretty sure this is an issue with the test being too picky and not a
bug, but the behavior in this situation is not well documented.

Despite the old comments, re-initing the msg_t leaks a refcount to
metadata in some situations.

v1_decoder looks like it isn't tested any more, but it seems like a good
idea to fix it because it has the exact same piece of buggy code
v2_decoder does.

It's nice to be able to disable libzmq's internal timeout when there's
another timeout in the test runner being used which gives nicer error
messages.

Problem: VS builds missing files, have warnings.

fix #1488 Heap buffer overflow in decoder

don't break STREAM socket ABI from 4.1.x to 4.2.0

Fix 1478: receive unsubscriptions in XPUB when verbose

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.

Fix windows build

fix #1447 Segfault or Abort after PR #1441

Fix compilation on mac.

Fix memory leak when creating a socket fails.

Previously, AddressSanitizer flagged leaks when running
tests/test_many_sockets.cpp.

Fix several missing msg_t::close calls.

I traced memory leaks found using AddressSanitizer down to these.

Fix test_proxy hanging occasionally by setting ZMQ_LINGER to 0.

Fixed #1477  corruption in "zero-copy" raw_decoder for payloads large…

Fixed wrong message::init arguments.