Autoproj next release: fix your XML before it's too late!

In an effort to make autoproj installation less problematic, I've
removed the dependency on nokogiri (and other libraries) for parsing the
manifest.xml files.

The side-effect of that change is that the new parser I'm using (REXML,
the standard Ruby XML parser) is a VALIDATING parser. Autoproj will
therefore choke on bad manifest.xml files, which do exist.

Run the script attached to this mail from the root of your autoproj
installation to find out which manifest.xml needs fixing.

For instance:

cd ~/dev
ruby ~/Downloads/test_xml_validity.rb

I'd like to publish the new autoproj before christmas ... you've been