[Rock-dev] Phasing-in Ruby 2.0+

[Sylvain Joyeux]

As we agreed a while ago, 15.03 would be the last release supporting
ruby 1.9 (which is already end-of-life if you are wondering).

This means that master will be open to ruby 2.0+ constructs. The major
improvement are keyword arguments (and thus the gradual phasing-out of
utilrb's validate_options):

  http://globaldev.co.uk/2013/03/ruby-2-0-0-in-detail/

What I am asking myself is whether we should recommend ruby 2.0 as the
ruby version for Rock 15.03 as well. (I've been running 2.1 for a year
or so now, personally). 2.0 should be forward-compatible with 1.9.

Autoproj should now do "the right thing" if you re-bootstrap an
existing install with

  rm -rf autoproj .gems
  /usr/bin/ruby2.0 autoproj_bootstrap git URL
  autoproj rebuild

Sylvain