[maven-release-plugin] prepare release 4.3
[maven-release-plugin] prepare for next development iteration
Merge pull request #637 from sharwell/release/4.3

Release/4.3
[maven-release-plugin] prepare release 4.3-opt
Merge branch 'release/4.3-opt' into optimized
Merge remote tracking branch 'antlr/master' into optimized