XInclude tests fail during build when using JDK 1.5

The XInclude test suite uses exact string matching to determine whether a test passed or failed. However, error messages can be unstable; they can vary between JDKs. In particular, several XInclude tests were failing because the exception message for a FileNotFoundException added a period to the end of the message in Java 1.5.

To fix this, we shouldn't be checking error messages beyond our control in the test suite.