(#18494) Ruby 2.0 support

This is a mostly small changes to get Puppet passing unit tests under Ruby 2.0.0-rc2.  Acceptance tests against Fedora 19 w/2.0.0-dev seem to mostly pass (one new error is unicode related, but in facter).

The main functional change is I've said that ActiveRecord-based storeconfigs for inventory data is unsupported under Ruby 2.0 (see d5e266c).  There were some odd errors coming from AR's associations code, but since Rails 3.0 is EOL and their 3.0 unit tests won't run on 2.0, I think it's safe to ignore as a target platform.

There remains one set of Racc warnings, which appear to be coming from naginator:

    racc/parser.rb:27: warning: already initialized constant Racc::Parser::Racc_Runtime_Versionr /home/dcleal/.rvm/rubies/ruby-2.0.0-rc2/lib/ruby/2.0.0/racc/parser.rb:183: warning: previous definition of Racc_Runtime_Version was here

I think it's because racc has been embedded in lib/puppet/external/nagios/parser.rb, then we're requiring it into puppet core, so it's duplicating various constants.  I don't know the best way of fixing this.