Multiple link wizards per page(single commit)

I have to use dokuwiki toolbar in my plugin but dokuwiki intitToolbar mechanism has one limitation. Altough you can create multiple texareas with wiki toolbars per one page - the link wiz window breaks everything. So I've decided to fix it and here is the result of my work. Applying this patch you can create as many textareas with toolbars per page as you wish and everything seems to work correctly.

From the technical point of view I've used javascript prototype to create multiple dw_linkwiz instances from a single object.