rrdtool: Update to 1.7.1

rrdtool: Update to 1.7.1

Disabled 'lua' because otherwise building failed.

I didn't find any place or reason where 'lua' was used by 'rrdtool', so it
was deactivated.

Disabling had no noticeable effects by now. Running.

Please note:
'/usr/lib/collectd/rrdcached.so' and '/usr/lib/collectd/rrdtool.so' have to
be updated, too.

Signed-off-by: Matthias Fischer <matthias.fischer@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>