Support for the PACKAGE VERSION syntax

Since 5.14, Perl has supported this syntax for declaring a version number for a package:

    package Foo 1.0 {
        ....;
    }

This pull request adds similar version declaration to the `class` and `role` keywords:

    role Foo 1.0 {
        ...;
    }
    class Bar 1.0 with Foo {
        ...;
    }