Fix glaring typos in RUN_DEPENDS.
Thou shalt obey ${PREFIX} no matter what nagios-plugins does, so create
the plugins directory if it doesn't exist.
Fix package list to use EXAMPLESDIR correctly.
Don't use bsd.port.(pre|post).mk unnecessarily.
Approved by: eik
Add new port nagios-silfreed-plugins, a set of SNMP oriented plugins for
Nagios from silfreed.net believed to work significantly better than the
bundled check_snmp plugin for most uses.