Expose zmq_curve_keypair via zmq_utils

asserts aren't appropriate for checking user input.

config for libsodium in alternate path, using CPP flags for both C and C...

include missing platform.hpp in curve_keygen

it was excluded, so HAVE_SODIUM would never be defined,
leading to curve_keygen always reporting "recompile with libsodium"

they are used by curve_keygen, but not available

This pull requests fixes building on SmartOS and possibly other Solaris-like systems

Updated CMake project for test_issue_566

Added test case for issue 566

* Tests dealer-to-router connection 100 times
* This was failing in ZMQ v4.0.0 RC1

Build/test errors on OS/X with clang++

Call flush after writing the identity message

Updated libzmq CURVE to track RFC 27

* The INITIATE command vouch box is Box[C',S](C->S') instead of Box[C'](C->S),
  as recommended by https://codesinchaos.wordpress.com/2012/09/09/curvecp-1/,
  to reduce the risk of client impersonation.

* Mirrors the change in libcurve and CurveZMQ specifications.

Fixed build for MSVC 2008

stdint.h is not available on all platforms

Bumped library version and age

Update configure: Allow libsodium to be installed in a custom path

Move away from port 8080 which is occupied on some boxes

Revert "Reference platform.h by ../src/platform.h - AIX is ignoring -I flags"

This reverts commit 015d9564.

Fixed packaging (makefiles were wrong)

Reference platform.h by ../src/platform.h - AIX is ignoring -I flags