Fix for munin-cgi-graph crash in trend and predict.

 - use get_field_name on the fieldnames for trend and predict.  A too long
   internal field name would make munin-(cgi-)graph crash.

 - bonus fix: use the label, and not the internal name, for the predict and
   trend labels.  (df graph will use "/home predict" instead of "_dev_vg0_home
   predict", or similar)
master: adding ":" to the allowed chars in CGI

":" is a valid char for an IPv6-enabled "ip_" plugin
Merge branch 'fix-ipv6' into stable-2.0
Merge branch 'trend_predict_crash' into stable-2.0
dev_scripts: automate async install

Also installs munin-async(d), so debugging it is eased.
master: re-enable debugging output in GraphOld.pm

Commit e0a1fe504d93021d9e2f2b8c2fc6eb2234474a64 added support for the --debug
so it could be launch with it.

This also adds the --debug behavior. It still doesn't log anything in normal
mode
Merge branch 'fix-debug-graph' into stable-2.0
asyncd: use the same rules as munin-update

munin-update does some squashing on invalid chars when using non-multigraph
plugins. This is done transparently when using the plain old TCP transport.

As munin-async(d) uses the spoolfetch transport that is multigraph-based, it
has the side effect not squashing the root plugin name. This patch squashes the
root plugin name in the same manner as done by munin-update.

It therefore enables to insert the munin-async(d) couple in-place to benefit
transparently.

Closes D:710529
ChangeLog for  2.0.15
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
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
Merge branch 'fix/d/710899' into stable-2.0