Accessibility: Add ARIA landmarks.

These are the modern equivalent of the "jump to content" link.

r2/r2/templates/reddit.html

@@ -132,7 +132,7 @@
       ##<div class="fixedwidth"><!--IE6sux--></div>
       ##<div class="clearleft"><!--IE6sux--></div>
       <a name="content"></a>
-      <div ${tags(id=thing.content_id)} class="content${css_class(thing)}">
+      <div ${tags(id=thing.content_id)} class="content${css_class(thing)}" role="main">
         ${content()}
       </div>
     %endif

r2/r2/templates/redditheader.html

@@ -29,7 +29,7 @@
 %>
 <%namespace file="utils.html" import="plain_link, img_link, text_with_links, separator, logout"/>
 
-<div id="header">
+<div id="header" role="banner">
   <a tabindex="1" href="#content" id="jumpToContent">${_('jump to content')}</a>
   ${thing.srtopbar}
   <div id="header-bottom-${'right' if c.lang_rtl else 'left'}">

r2/r2/templates/searchform.html

@@ -53,7 +53,7 @@
   <p><a href="http://www.reddit.com/help/search" id="search_showmore">${_('advanced search: by author, community...')}</a></p>
 </%def>
 
-<form action="${add_sr('/search')}" id="search">
+<form action="${add_sr('/search')}" id="search" role="search">
   <input type="text" 
          %if thing.prev_search:
            value="${thing.prev_search}" style="color:black"