dist.ini; skip UnusedVars, fix deplist
improve Constants POD

	modified:   lib/POEx/ZMQ/Constants.pm
	modified:   tools/zmq_constants.pl
kill ->has_filter

	modified:   lib/POEx/ZMQ/Socket.pm
warn_if_error; cluck instead of warn

	modified:   lib/POEx/ZMQ/FFI/Role/ErrorChecking.pm
POD