Removed contrib/tarballs/hopcroft-plugins.tar.gz. This is archaic, anachronistic, unmaintained and humblingly embarrassing.

git-svn-id: https://nagiosplug.svn.sourceforge.net/svnroot/nagiosplug/nagiosplug/trunk@505 f882894a-f735-0410-b71e-b25c423dba1c