Tests for XML and Namespaces

I have added tests to the test suite for the errata since XML 1.0 3rd
edition and Namespaces 1.1.  There were already tests present for the
errata to Namespaces 1.0 that were incorporated in 1.1.  There are
some extra errata for XML 1.1 but I don't think they need tests.

If you only wish to run the new tests, the directories are
.../eduni/namespaces/errata-1e and .../eduni/errata-3e.

RXP fails one of the tests, because it treats all undeclared entities
as fatal errors rather than some being mere validity errors.

-- Richard