Parenexpr-20.xq involves a subterm (/) (I think this is the only example
of a leading / in a path expression in the test suite)

xq2xqx and the test parser applet both encode this as

         <xqx:parenthesizedExpr>
                  <xqx:rootExpr/>
                </xqx:parenthesizedExpr>


Which seems to be the natural XqueryX encoding, given that XqueryX has a
rootExpr element. However the supplied XqueryX version of this test expands /
and encodes this subterm as (the XqueryX equivalent of) the expansion of /
if thought of as abreviated syntax. The XQueryX specification is currently
rather inconsistent in whether abbreviated syntax should be expanded or not,
but in the test suite I think it's best to keep the two forms as close as
possible, so that the tests are testing the same thing, and that rootExpr should
be used (or removed from XQueryX if it shouldn't be used).

                              <xqx:parenthesizedExpr>
                                <xqx:pathExpr>
                                  <xqx:argExpr>
                                    <xqx:treatExpr>
                                      <xqx:argExpr>
                                        <xqx:functionCallExpr>
                                          <xqx:functionName
xqx:prefix="fn">root</xqx:functionName>
                                          <xqx:arguments>
                                            <xqx:pathExpr>
                                              <xqx:stepExpr>
                                                <xqx:xpathAxis>self</xqx:xpathAxis>
                                                <xqx:anyKindTest/>
                                              </xqx:stepExpr>
                                            </xqx:pathExpr>
                                          </xqx:arguments>
                                        </xqx:functionCallExpr>
                                      </xqx:argExpr>
                                      <xqx:sequenceType>
                                        <xqx:documentTest/>
                                      </xqx:sequenceType>
                                    </xqx:treatExpr>
                                  </xqx:argExpr>
                                </xqx:pathExpr>
                              </xqx:parenthesizedExpr>
                            </xqx:filterExpr>