No meaningful changes.

Now it is possible to register multiple classifiers with the same type.

This reverts commit e0483657ff.

Many changes to advanced statistic and meta-classification logic.
Add example of complex meta-classification.

* Add labels support to the statfiles (would be used for meta-classification)
* Rewrite exim spam.c patch to work with both rspamd and SA by using 'variant=rspamd' option
  in spam_server line.

Add apache license for regexp that were delivered from SpamAssassin project.
Fix debian/copyright for src/dns.c.

Fixed several memory leaks with modern glib.
Fixed memory leak in dkim code.
Fixed a problem with static global variables in shared libraries.

* Add lua utility library for basic utils.
* Fixes lua_buffer code.
Fix lua loading error.
Added some other lua utility functions.

 - pool allocator is now thread-safe
 - lua subsystem now holds lock to avoid lua stack corruption
 - events subsystem now using conditional variables to wait for async_threads
 - insert_result is thread-safe now

Update to 0.4.3.

* Fix build of rspamd with CMAKE_BINARY_DIR differs from CMAKE_SOURCE_DIR
Rework include style.

Fix problems found by static analyzing.

Fix call of classifier pre-callback.

Fix call of pre callbacks for a classifier.

Now all comments in commit logs beginning with '*' would be included in changelog, so
important changes would be separated from small ones.

  - independent and customizeable buffering
  - line buffering
  - errors handling support
  - custom (ip based) debug
  - append function name automaticaly (based on __FUNCTION__)
  - add some logic to logs system

TODO:
  - add properties to get all parameters of input task
  - add properties to statfile object
  - add some normalization function for calling from classify process
  - document changes