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.

Fix another degradation, CPU maxes out when POLLOUT is set

Fix another degradation, CPU maxes out when POLLOUT is set because poll exits on POLLOUT and doesn't wait for POLLIN.

Fix degradation from #1382, POLLOUT was tested but not requested

Problem: missing brackets

doc/zmq_socket.txt: Remove note about ZMQ_PAIR being experimental.

Problem: libzmq has temp debug printf

libzmq: Fix pkg-config files for static linking

Libzmq uses C++ standard library features, so users of it should link
against that as well when statically linking.

Add it to Libs.private so users using pkg-config automatically gets the
correct linker flags.
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

Some test fail to build targeting less that Windows Vista

When targeting a version of Windows less than Windows Vista, the
security tests fail to build. Added a check for Windows version
and substituted inet_pton for inet_addr. Fixes libzmq issue #1396.