create a perl error document that returns different urls/pictures based on file type.
Will be used as ErrorDocument 404 in apache 2.x.
If the missing file is .gif, .jpg, .png, return /picture.gif.
If missing document is .html, .htm or .jsp, return /404.jsp.
Must work with mod_jk(1.2.x) and the jkMount /*.jsp inside virtualhost of apache 2.x.