RACR-meta: integration of attribution meta-facilities

[christoff-buerger]

So far, only the analyses of abstract syntax tree specifications, the instantiation of respective trees and the analyses of respective attribute specifications is realised using a RACR-based compiler. The instantiation of attribute instances throughout tree construction and rewriting is still done using the original non-metacircular RACR implementation. First analyses regarding attribution updates w.r.t. context changes are given by the attribution-factory attribute. Though, the attribute is not used yet.

To do also attribute instantiation and maintenance requires full-fledged meta-circularity, including meta-instantiation as proposed by issue #62.