plugins/ntp_: fix parsing older ntpq output

Apparently ntpq 4.2.4p5 output is a little different from modern versions. This commit makes the
plugin work either way. Thanks for the report and patch by Eugene in
<http://sourceforge.net/mailarchive/message.php?msg_id=30855572>.
master: fix warning in GraphOld.pm

Commit 594b07b14e24c262358ec0edfec8e7771bce5ad3 re-enable debugging output in
GraphOld.pm, but emits a spurious "WARNING"

This commit fixes it.
Merge branch 'fix-debug-graph' into stable-2.0
travis: stable-2.0 is the branch to test (was master)
tests: Module::Build is duplicated in .travis.yml
tests: Net::Server dep was missing in .travis.yml
tests: Use only IRC notifications for TravisCI
ChangeLog: 2.0.16
Merge tag '2.0.16' into debian

2.0.16
Update changelog
Release 2.0.16-1 for Debian unstable
p/df: also ignore devtmpfs

devtmpfs should be excluded by default also.

I explicitly don't exclude tmpfs as it is quite useful as metric.

Closes: D:710899
plugins/df: ignore devtmpfs. Cherry picked ab42e8b as efe4526 from  upcoming 2.0.17. (Closes: #710527)
Add libcgi-fast-perl as alternative suggests. (Closes: 711272)
release as 2.0.16-2 to sid
Correct bug number for 2.0.16-2 upload