Fixed some state issues where event collisions where happening.

Created a way to prune “interval” messages by default (not needed for Logstash events).
Added more types (old-style time and interval, message and severity)
Merge branch 'master' of https://github.com/logstash/logstash

# By Jordan Sissel
# Via Jordan Sissel (3) and Aaron Mildenstein (1)
* 'master' of https://github.com/logstash/logstash:
  Invoke jruby compilation from ruby code, not via jrubyc
  Have 'release version' computation include the git hash only on .dev versions
Merge pull request #809 from untergeek/master

Fixed some state issues where event collisions where happening.