Add support for latexport in Anchor plugin

[jean-michel-gonet]

Why?

• To be able to use the anchor feature

Condition of satisfaction

• Anchor has to call latexport with the description of the anchor.
• Here is the code snippet that goes into anchor/syntax.php

    function render($mode, Doku_Renderer $renderer, $data) {
        if ($mode == 'latexport') {
            $renderer->anchor($data[0], $data[1]);
        } else {
            $renderer->doc .= '<a name="' .htmlspecialchars($data[0]) . '">' .htmlspecialchars($data[1]) . '</a>';          
        }
    }

[jean-michel-gonet]

Added in documentation