Add Interesting option for thresholds

Hi everybuddy

This patch add a new keyword called "Interesting" on thresholds.

By default all thresholds are interesting, so a missing notification will
dispatched on missing values. Setting the Interesting option to false avoid
to send this notification even if some values are missing.

It's usefull when you gather a lot of information from the same source, and
a missing reader could result in a big number of notifications. Furthermore
you can use this keyword to prevent missing messages on values which are not
more interesting to known if they are missing (for example a df over a disk
which usually append to the system during a backup, and them is removed).

Regards,
  Andres
Complete the collectd.conf man page.

Hi people!

This patch improves the documentation in the collectd.conf(5) man page about
threshold keywords, including Hysteresis, Hits or Interesting flags.

Regards,
  Andres
Add custom message for threshold and missings.

Hi everybuddy

Add two new options in thresholds, the Message which can define a custom
message for thresholds and MissingMessage, which define a custom message for
missing interesting values related with that threshold.

This work is heavly based on previously custom message patch publishded by
Taizo ITO on Mar-2010 [1]. The code was modify to add more patterns and keep
compatibility with target_notification syntax. Also now we have
a MissingMessage too.

The pattern matching code was moved to a new function in utils_threshold.c
(ut_build_message) which create the message string.

New patterns:

	%{ds:<name>} returns values for ds called "name", as target_notification
	does.
	%{value} return the offending value for the threshold.
	%{data_source} return the datasource name for offending value
	%{hysteresis} return the hysteresis parameter value
	%{hits} return the hits parameter value

[1] http://www.mail-archive.com/collectd@verplant.org/msg00569.html

Thanks again to Taizo for the previously work :)

Enjoy!
Merge remote branch 'upstream/master'

Conflicts:
	src/utils_threshold.c: related with octo's cf_util_get_flag
Add custom message for threshold and missings.

Add two new options in thresholds, the Message which can define a custom
message for thresholds and MissingMessage, which define a custom message for
missing interesting values related with that threshold.
src/utils_{cache,threshold}.c: Add/update copyright information for Andrés.
src/utils_threshold.c: Improve the replacement macros.
src/utils_threshold.c: Add missing folding markers.
src/utils_threshold.c: Some (whitespace only) coding style changes.
src/utils_threshold.c: Replce some of the config functions by their generic version.
src/utils_cache.c: Resolve macros that are used only once.
src/utils_cache.c: Don't free "name_copy" twice.

It's been freed unconditionally above, so there is no need to call free again.
This didn't result in an error since "sfree" NULLs the pointer.
Merge remote branch 'upstream/master'
Add redis plugin.

This commit adds a new redis plugin, which connect to a number of redis
server and get information about their status, using the libcredis > 0.2.2
library. The plugin get the following information:

* bgsave_in_progress
* change_since_last_save
* connected_clients
* connected_slaves
* total_command_processed
* total_connection_received
* uptime_in_seconds
* used_memory

Here is an example of configuration file:

<Plugin redis>
	<Node example>
		Host "localhost"
		Timeout 2000
	</Node>
</Plugin>

And the output of rrdtool plugin must be something similar to this:

redis-example/bgsave_in_progress.rrd
redis-example/changes_since_last_save.rrd
redis-example/connected_clients.rrd
redis-example/connected_slaves.rrd
redis-example/total_commands_processed.rrd
redis-example/total_connections_received.rrd
redis-example/uptime_in_seconds.rrd
redis-example/used_memory.rrd

Enjoy! :)
Merge branch 'master' of git://github.com/octo/collectd
Merge branch 'master' of git://github.com/octo/collectd
Merge remote branch 'upstream/ad/msg'

Conflicts:
	src/utils_cache.c
	src/utils_threshold.c
Merge branch 'ad/redis'

Conflicts:
	src/Makefile.am
	src/collectd.conf.pod
	src/redis.c
Fix a number of minor bugs.

- The Port configuration option is a string, not a number. Fix
  documentation.

- Fix a bad status assignement in port parser.

- Remove default node. Now node is mandatory to prevent
  duplicates in tree.

- Update configuration example too.
Merge branch 'ad/redis'