Adapt coverage to Saxon 9.3+

[GoogleCodeExporter]

Excerpt from 
http://groups.google.com/group/xspec-users/browse_thread/thread/d0123335f16fe3e6
 (message from Sep 26):

"""
  Coverage relies on a Java class which is an implementation of
Saxon's TraceListener.  The name of this interface has changed
between 9.2 and 9.3 so it is not possible to have a portable
class without knowing the version of Saxon.

  Furthermore, the stylesheet that formats the coverage report
uses saxon:line-number() which is not available neither in 9.3
nor 9.2 (I am not sure excatly where it stopped to be available
in the free edition of Saxon, I bet in 9.2 when Saxon B switched
to Saxon HE).

  For the first point (the Java class), I guess we can say that
Saxon 9.3 has been out for more than one year now, so it is time
to switch to it.  For the second point (the saxon:line-number()),
we need to investigate further and find an alternative (that
could be an extension function as we already depends our own Java
classes for coverage).
"""

Original issue reported on code.google.com by fgeorges on 26 Sep 2011 at 3:38