add Haiku support

* link against libnetwork.so for network functions.

Problem: REQ socket with ZMQ_REQ_RELAXED does not report ZMQ_POLLOUT when queried for events after first message.

Problem: REQ socket with ZMQ_REQ_RELAXED does not report ZMQ_POLLOUT when queried for events after first message.

Solution: Check for strictness before returning false if no reply has been received.

Problem: Sometimes on OSX we get ETIMEDOUT instead of EAGAIN

Solution: Update errno value after calling usleep()

Optimize select on Windows; reduce code duplication in select_t

Solution: unified Windows & non-Windows code further

Solution: reduced code duplication by introducing local variables and
new function trigger_events

same fds

Solution: cache results of get_fd_family

Problem: wsa_events are initialized/destroyed within every loop

iteration even if not used

Solution: Move wsa_events closer to usage

Change ZMQ_THREAD_AFFINITY to ZMQ_THREAD_AFFINITY_CPU_ADD/REMOVE

Change ZMQ_THREAD_AFFINITY to ZMQ_THREAD_AFFINITY_CPU_ADD/ZMQ_THREAD_AFFINITY_CPU_REMOVE. Avoid prefix thread names when no prefix was set.

Partial Windows XP support

Problem: one missed optimization opportunity for blob_t map lookup

Solution: create referencing blob_t

Problem: use of std::map::insert is inefficient

Solution: use std::map::emplace instead, where available

Problem: description of return value is cloned from zmq_atomic_counter_new

Solution: provide correct description

Fixes #2789

* Problem: excessive memory allocations around blob_t

Solution: redefine blob_t as a custom type, and use reference/move
semantics where possible

* Clarify usage of zmq_close

Problem: comment before sndtimeo/rcvtimeo does not specify dimension

Solution: add "milliseconds"

Problems: DRAFT build broken in CentOS 6, missing bits in documentation

added note concerning issue 2788 to INSTALL

Solution: define __STDC_LIMIT_MACROS in test_timers.cpp before
including testutil.hpp so that the definitions are included

added libiphlpapi to PKGCFG_LIBS_PRIVATE for static mingw builds

Solution: print unsigned integers instead of size_t to avoid the error:

  error: ISO C++ does not support the 'z' gnu_printf length modifier

due to very old version of GCC.

Solution: mention that the STATISTICS command returns a message with 8
frames

Solution: fix it

Increase details in docs

* Add ZMQ_THREAD_NAME_PREFIX ctx option