Reset metadata for outbound messages

Bugfix wrong CMakeLists.txt after rename of file

Documentation patches

Renamed test case to actually explain what it's testing, and cleaned up
the code a little.

Solution: change setsockopts on printable keys to expect 41, nor 40
bytes. Code still accepts 40 bytes for compatibility, and copies the
key to a well-terminated string before using it.

Fixes #1148

Code cleanup

Provide socket option for pub sockets to not silently drop message

Document altered HWM behaviour when ZMQ_ROUTER_MANDATORY is set.

Add test for HWM behaviour for mandatory ROUTER sockets over tcp

moved root CMakeLists.txt tests config to tests/CMakeLists.txt

Update zmq_msg_get(ZMQ_SHARED) to return true for type_cmsg messages

define encoding for message metadata to be UTF8

use enum retired_fd instead of -1

clarifies that these are text fields,
and removes ambiguity about how to create proper
text object from stored bytes.

Problem: does not install man pages correctly when out of tree

Solution: fix Makefile.am

As per Richard Sharpe on zeromq-dev.

z/OS: Updated to build libzmq git master

Updated:
    builds/zos/README.md: Updated with portability notes resulting
       from building zeromq/libzmq/master as of 2014-07-23 on z/OS
       UNIX System Services.

       Current z/OS UNIX status: all expected tests pass, except
       "test_proxy", which hangs and times out.

Updated:
    src/thread.cpp: On older z/OS UNIX System Services,
        pthread_{get,set}schedparam is not present (searching the
        Internet suggests it may be present in later version than
        the one being used for z/OS UNIX System Services porting).

        Make zmq::thread_t::setSchedulingParameters() a no-op on
        z/OS UNIX System Services.

    NOTE: pthread_{get,set}schedparam appear to have been introduced
    by POSIX.1-2001 or IEEE 1003.1-2004 so may not be universally
    available, and thus more platforms may need this "no-op" treatment.

Updated:
    builds/zos/runtests: Extract tests to run from tests/Makefile.am
      at runtime, rather than hard coding tests list (to simplfy
      later maintenance).  test_*_tipc is excluded as BUILD_TIPC is
      not defined on z/OS UNIX System Services.  XFAIL_TESTS are also
      excluded, following current logic in tests/Makefile.am

Updated:
    builds/zos/cxxall: Defines ZMQ_HAVE_ZOS for platform portability;
        define ZMQ_USE_POLL _instead_ of ZMQ_FORCE_POLL, due to change
        in src/poller.hpp since ZeroMQ 4.0.x branch

Updated:
   tests/test_connect_delay_tipc.cpp
   tests/test_sub_forward_tipc.cpp
   tests/test_term_endpoint_tipc.cpp

Updated:
    src/metdata.hpp: Remove explicit "const" from key of std::map<>
       because the key is implicitly const already (see
       http://en.cppreference.com/w/cpp/container/map and
       http://www.cplusplus.com/reference/map/map/).

On some platforms (such as z/OS UNIX System Services) explicitly
declaring the map key as "const" causes template expansion errors
as it tries to create separate allocators for "const const std::string"
and "const std::string" only to find that they clash.  (Presumably
some compilers collapse these into one earlier.)

There are no template expansion errors if the map key is left to be
implicitly const.