Upgrade JavaCC Maven plugin to 3.1.1

[NiccoMlt]

Request:
Upgrade the JavaCC Maven plugin from version 2.4 to the latest stable, 3.1.1.

Context:

• The plugin version is set by the javacc-maven-plugin.version property in the parent POM.
• Version 3.1.1 introduces support for JavaCC 8.x and drops support for JavaCC 6.x. See release notes and changelogs from 2.x releases.

Migration steps:

1. Update the property in pom.xml: <javacc-maven-plugin.version>3.1.1</javacc-maven-plugin.version>
2. Audit all grammar files (src/main/javacc) for syntax incompatible with JavaCC 7/8.
3. Verify build and tests work after upgrading, as JavaCC syntax or plugin options may need adjustment.
4. Reference upgrade changelogs for any configuration changes or migration notes:
   • 3.1.1 release
   • 3.1.0 release
   • 3.0.1 release
   • Older 2.x changelogs

Benefit:

• Bugfixes and compatibility with newer JavaCC releases.
• Future-proofing parser development for Java 8+ and modern JavaCC grammar options.

If problems arise with grammar syntax, reference JavaCC documentation and JavaCC Maven plugin documentation.