Grammar forking can be removed

[kaby76]

There are a number of grammars that are forked, e.g., java/java9, antlr/antlr4, javascript/ecmascript, python/python, sql/plsql, ...

These forked grammars can be collapsed using the transformGrammar.py hack. Using this transform, which is already plugged into the build, can be used to minimize grammars that are not being consistently maintained across all targets (e.g., here, where one .g4 was modified, but another that is target-specific was not).