libzmq2: sync with FreeBSD ports

* fix package name -- cheers to @koobs
* upgrade to 2.2.0
* support staging
syslogd: adjust name for pkg-query(1) querying ;)
php-zmq: adjust port for pkg-query(1) and more

Also fixes the library dependency so that FORCE_PKG_REGISTER is
not needed.
mpd4: staging is a bitch