Require a later version of XML.  The last bug was due to an XML change, 
so if a user had a previous version of XML, the new version of getEarnings would not work.  
Some tests added, but they would not have helped in this situation.


git-svn-id: svn://scm.r-forge.r-project.org/svnroot/twsinstrument/pkg/qmao@412 edb9625f-4e0d-4859-8d74-9fd3b1da38cb