cppzmq: new package

Now that zeromq has been bumped to version 3.2.2, we need to provide the
C++ binding using a separate package. The cppzmq package provides a simple
single-header C++ binding.

Signed-off-by: Simon Dawson <spdawson@gmail.com>
[yann.morin.1998@free.fr: add comment about no license file]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>