chicken: revamp recipes

chicken: revamp recipes

To allow easy usage of chicken, in embedded environments, we have done
some refactoring in the packages:

 - split it up to chicken, libchicken and libuchickenl
 - drop 2.6 version since no distro depends on that and is not
   commonly used anymore;
 - generalize .inc file to be usable for 3.x and 4.x versions;
 - add new 4.2.0 release,
 - use INC_PR.

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>