Fix windows build

test zmq_msg custom free-function

new allocation caused reference counters to lose track on copy

don't check POLLOUT for single-socket proxies

Fix initialization order.

Fixes #1431.

Enable install of man pages when BUILD_DOC is not set by shifting INS…

Enable install of man pages when BUILD_DOC is not set by shifting INSTALL_MAN outside of BUILD_DOC's if/endif

Update documentation for zmq_setsockopt.

Pull request #1426 now allow for changing the watermark
after and connect() or a bind(). This patch reflect the
change in the documentation.

Also closes #1416.

Allow changing of high water marks after connection is established

Fixed executable name in the usage string

Fix xpub test to set hwm before bind.

Fail ZMQ_SNDHWM and ZMQ_RCVHWM setsockopt if already connected.

Problem: tests/test_socketopt_hwm fails and breaks CI

Solution: mark this as XFAIL

Introduce a failing test against zmq_setsockpt().

Problem: zmq_setsockpt() returns success when changing the
HWM after a bind or connect() even though the call has no effect.

Solution: Introduce a failing test a reminder we need to patch it.

Zero copy message receive in v2_decoder

Construct messages from a reference-counted buffer allocated once
per receive instead of copying the data.

With a msg_t size of 64 bytes, it becomes possible to embedd the content_t's members
struct for large messages directly in the msg_t. This saves the dynamic allocation
of content_t obejcts when using msg_t::init_data.

content_t contains a zmq::atomic_counter_t object which is not a POD in C++98
and thus it cannot be used as a member of the union u. To bypass this, C++11
is used which has relaxed rules for POD and atomic_counter is a C++11-POD. An
alternative would have been to make atomic_counter a classical POD by removing
constructors and all private member functions, i.e. have a struct and free functions
to manipulate it.

A new msg_t::init function is added which decides to either to copy the data for size<64 bytes
or use msg_t::init_data to do zero-copy initialization.

Fixes to README

Problem: source file headers are somewhat confusing about LGPLv3

Of course people still "can" distributed the sources under the
LGPLv3. However we provide COPYING.LESSER with additional grants.

Solution: specify these grants in the header of each source file.

HPUX build and gmake check issues solution. Fixes #1412 

Fixed out-of-bounds access when releasing socket handles.