Altered Host: header so that it does not include 443 on https requests. 

This was confusing some webservers, specifically the one at data.ox.ac.uk. 

The previous code showed the port number on https unless the port number was '80'. I've altered it to not include 443 in host requests when using https.

The following test should show the fix in action.

<?php

require_once( "arc/ARC2.php" );

$uri = "https://data.ox.ac.uk/doc/vacancy/105043.rdf";
$parser = ARC2::getRDFXMLParser();
$parser->parse( $uri );

$errors = $parser->getErrors();
if( sizeof($errors) )
{
        print join( "<br />\n",$errors)."<br />\n";
}
else
{
        print "loaded ".sizeof( $parser->getTriples() )." triples<br />\n";
}