[Pharo-dev] XML writer in the default image

As reported a while ago (https://pharo.fogbugz.com/default.asp?7412#80347), the TestRunner is crashing when test failures accidentally spit out XML sensitive characters: https://ci.inria.fr/pharo/view/all/job/Pharo-3.0-Regression-Tests/304/VM=vm,... I don't really see a reason to generate XML by concatenating strings, so I wonder whether we could include the XMLWriter in the default image? This way I could finally fix the HDTestRunner with very little effort.