This would be fairly simple to accomplish. First off, in the nagios-core ebuild, since we are using --with-mysql-xdata and --with-postgres-xdata, there is no need to specify the other 5 --with-${dbtype}-* commands. The --with-*-xdata command means all of the others. Also, nagios-plugins should, at minimum, copy the contrib/check_nagios_db.pl file to the nagios plugins directory when USE=mysql or USE=postgres, otherwise it is not possible to monitor a Nagios that uses a database for its backend.
updated nagios-core.
added contrib plugins, and as a special case check_nagios_db.pl is inserted directly to libexec when use mysql/postgres.
Thanks... =]