backport r1379321: Note that using rewrites with a file-path substitution in a...

        you specify a <em>Substitution</em> string of

        <code>/www/file.html</code>, then this will be treated as a

        URL-path <em>unless</em> a directory named <code>www</code>

        exists at the root or your file-system, in which case it will

        exists at the root or your file-system (or, in the case of 

        using rewrites in a <code>.htaccess</code> file, relative to

        your document root), in which case it will

        be treated as a file-system path. If you wish other

        URL-mapping directives (such as <directive

        module="mod_alias">Alias</directive>) to be applied to the