Make 'if "something" not in [nonexistent] { ... }' succeed

My argument is checking for the absence of a value in a field that doesn't
exist should return true, currently it is false.

This fixes the case where an event which has never been tagged now works with
this logic:

    grok {
      ...
    }
    if "_grokparsefailure" not in [tags] {
      ...
    }
Small enhancements to netflow codec

- Add configurable target field for netflow fields, defaults to "netflow"
- Add configurable filter to restrict which versions to accept
Fix memory leak in syslog input. (tcp server)

Remove the client from the clients list when the connection is closed.
fixed unix input: syntax error
Merge pull request #682 from bodgit/notin

Make 'if "something" not in [nonexistent] { ... }' succeed
Merge pull request #686 from bodgit/netflow

Small enhancements to netflow codec
Additional csv option for quote_char

This will allow users to configure a different quoting char in cases where the data may not exactly fit the csv standard.

A common example may be to completely ignore the quote char, and to do this a null \x00 char can be used instead.
Another example may be csv with ' as the quote char instead of "
Add test for default csv quote_char double quote "
Merge pull request #725 from markabey/csv_quote_char

Csv quote char
Merge pull request #720 from nikicat/fix-unix

fixed unix input: syntax error
since the plugin's name changed to collate, update the comments and method name, vars to collate, to keep consistent
Break out json into json_lines so that users streaming json can use the line delimited codec and users using message based transports i.e. redis can still use a codec without requiring the message end in '\n'
Add more descriptive docs for json/json_lines codecs
Allow output plugins to declare that, for a given configuration, workers are
not supported. Such reasons could include inability to share a resource
(like a listening socket, etc). This declaration will force a
single-worker setting and allow logstash to warn the user instead of
aborting.
Try to fix any @timestamp values if someone mucks with that field value
and turns it into a string through the json filter.
purge old and long-since-deprecated amqp plugins
- Include a (hopefully) better warning message when using an output
plugin that doesn't support workers.
- Remove worker_setup_skip hackery; not needed.
- update file and zeromq workers_not_supported settings
Be more obvious that worker count is ignored but otherwise work will continue
tcp in server mode doesn't support workers.