Eclipse OCL (Object Constraint Language) 2020-12 (6.13.0)

This minor release fixes a few bugs. Behind the scenes UI-based functionality responds to the platform migration to Java 11 and starts the migration away from the deprecated old to new Xtext infrastructure. The full migration was retracted at the last minute since the prototype of a new declarative serilaizer/formatter was not adequately tested and failed some tests. The editor for the Idioms DSL that configures the new serializer/formatter is provided.

(The work on Bye Bye invalid was still not ready in time for 2020-06; Xtext migration more important.)