Provide ZMQ::Socket->zmq_version proxy method

	modified:   lib/POEx/ZMQ/Socket.pm
	modified:   t/poex/zmq/socket.t
BAIL_OUT on bad linker search path in t/00_available

	modified:   t/00_available.t
don't bother trying to terminate sockets & contexts if $in_GD

	modified:   lib/POEx/ZMQ.pm
	modified:   lib/POEx/ZMQ/FFI/Context.pm
	modified:   lib/POEx/ZMQ/FFI/Socket.pm