[slf4j-dev] Plan for SLF4J 2.0

[Joern Huxhorn]

I've updated my branch at http://github.com/huxi/slf4j/tree/slf4j-redesign

I documented Message and implemented an AbstractMessage (that's  
already performing the lazy initialization and caching of the  
formatted message).
ParameterizedMessage and JavaUtilFormatterMessage are now extending  
this AbstractMessage instead of implementing that behavior manually.

Cheers,
Joern.