New L1/L2/L3 Core and L3 XPath tests

I've added some tests based on coverage analysis under bug 401.  The 
most significant are a series of approximately 19 tests in L3 Core 
(domconfig*) that test DOMConfiguration.getParameter/setParameter and 
canSetParameter for each property defined in L3 Core.  Additional tests 
will need to be added to check that they actually accomplish what they 
should.

I've also fixed the test failure with nodegettextcontent14 (bug 461) 
from the conversion of XHTML data files and added nodegettextcontent19 
to check that element content whitespace is stripped from textContent.