Added the ability to define new methods for built-in objects through the 'Obj.def_method("name", {})' interface.

Example:

    # Define the 'în_litere_mici' method for Strings
    String.def_method("în_litere_mici", { |str|
        str.lc
    });

    say "OLD".în_litere_mici;

    # Define the 'upperCase' method for Arrays
    Array.def_method("upperCase", { |arr|
        arr.map{|item| item.uc}
    });

    say ["a", "b", "c"].upperCase.dump;