Tango 9 lts remove zmq hpp

[bourtemb]

Remove zmq.hpp from tango-9-lts (#266)
Add CPPZMQ_BASE CMake optional variable

[t-b]

@bourtemb Is cppzmq now a required dependecy? If yes cmake should also complain if it could not be found or?

[bourtemb]

Well, zmq.hpp file is required.
On Debian it is distributed with zmq Debian packages.
On some other platforms, it might be independent.
Maybe we should add a CHECK_INCLUDE_FILE line to ensure it is available on the system and give a nice message explaining this requirement if the file is not found....

[t-b]

Maybe we should add a CHECK_INCLUDE_FILE line to ensure it is available on the system and give a
nice message explaining this requirement if the file is not found....

yes that sounds good!

[t-b]

@bourtemb THanks, I've just tested it here locally and it works.

[bourtemb]

@t-b Thank you very much for your feedback and for having taken the time to test it.

[bourtemb]

Closing this PR since it is now handled by PR #421