Move socket_base.hpp and err.hpp after poll.h include

These two headers also include zmq.h somewhere in their dependency
chain, so must be included after poll.h is included for builds to work
on AIX.
Merge pull request #48 from vortechs2000/fix_aix

Fix Build Regression #449: Move socket_base.hpp and err.hpp after poll.h include
Resolve LIBZMQ-417

Ref: https://zeromq.jira.com/browse/LIBZMQ-417
Resolve LIBZMQ-452

Ref: https://zeromq.jira.com/browse/LIBZMQ-452
Cleanups to man pages
Merge pull request #49 from hintjens/master

Backported fixes for LIBZMQ-452 and LIBZMQ-415
Resolve LIBZMQ-447
Merge pull request #47 from steve-o/master

Improve PGM build integration for Windows
Merge pull request #51 from hintjens/master

Backported fixes for LIBZMQ-447
Resolve LIBZMQ-458

Ref: https://zeromq.jira.com/browse/LIBZMQ-458
Merge pull request #52 from hintjens/master

Backported fixes for LIBZMQ-458
Fixed formatting in man page
Merge pull request #53 from hintjens/master

Fixed formatting on zmq_getsockopt.txt
Resolve LIBZMQ-464
Merge pull request #54 from hintjens/master

Backported fixes for LIBZMQ-464
Older versions of C compilers don't like C++ comments

There's no need to exclude older compilers by putting C++ style
comments in the C API header.

Signed-off-by: AJ Lewis <aj.lewis@quantum.com>
Merge pull request #55 from vortechs2000/remove_cpp_comments_from_zmq_h

Older versions of C compilers don't like C++ comments
Resolve LIBZMQ-459

Ref: https://zeromq.jira.com/browse/LIBZMQ-459
Merge pull request #56 from hintjens/master

Backported fixes for LIBZMQ-459
Backported fix for ZMQ-465