Added version and mainClass attributes to <jar> task.

[craigpell]

Added version and mainClass attributes to task, to set binary attributes of a modular jar file. For Ant 1.10.x. Addresses these tickets: https://bz.apache.org/bugzilla/show_bug.cgi?id=62772 https://bz.apache.org/bugzilla/show_bug.cgi?id=62789

[asfgit]

Can one of the admins verify this patch?

[asfgit]

Can one of the admins verify this patch?

[asfgit]

Can one of the admins verify this patch?

[asfgit]

Can one of the admins verify this patch?

[jaikiran]

this is ok to test

[asfgit]

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[asfgit]

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[jaikiran]

Thanks @craigpell, this is a very good enhancement and the code looks very good too. I do have some suggestions/questions about some of the new classes, but I haven't had a chance to fully review this PR. I'll take a more closer look at this one in the next few days and will merge or update this PR with my suggestions/questions.

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Refer to this link for build results (access rights to CI server needed): https://builds.apache.org/job/Ant%20Github-PR-Windows/121/

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[jaikiran]

While you are here, a quick suggestion/question - given that these changes are related to Java modules in general and there probably will be more such enhancements for modules, maybe we should rename the newly added org.apache.tools.ant.util.jarattr package to org.apache.tools.ant.util.modules instead? I don't have a strong opinion on it, so if you want to use the current package name that you chose, that's fine by me.