[maven-release-plugin] prepare release 4.2.1
[maven-release-plugin] prepare for next development iteration
Merge pull request #519 from sharwell/release/4.2.1

Release/4.2.1
Reference com.tunnelvisionlabs release of antlr4-annotations
[maven-release-plugin] prepare release 4.2.1-opt
Merge remote-tracking branch 'antlr/master' into optimized