testlib: open issues for xunitxml test logging

The xunitxml logger seems to be based on an old version of junit, where the schema doesn't have the concept of a test being skipped, and so skipped tests are shown in comments in the xml output and in the <system-err> tag, which is supposed to show a dump of the stderr stream for the test. Tools that parse the xml output will probably ignore the stuff in comments, so it will look like some tests weren't run.

There are a couple of newer definitions of xunit format that we may want to consider implementing:

• https://gist.github.com/959290
• http://xunit.codeplex.com/wikipage?title=XmlFormat

These new schemas add the capability to handle skipped tests and add a few other fields that may be of interest, e.g. hostname on which test was run, timestamp of start of test, time taken by test.

finally, unlike plain-text, xml and lightxml output formats, xunitxml does not currently show a test result for each data row of a data-driven test. The new schemas may allow this.