Add support for scope attribute on td and th.

Signed-off-by: Edward Z. Yang <ezyang@mit.edu>

NEWS

@@ -12,6 +12,7 @@ NEWS ( CHANGELOG and HISTORY )                                     HTMLPurifier
 4.3.1, unknown release date
 # URI.Munge now munges URIs inside the same host that go from https
   to http.  Reported by Neike Taika-Tessaro.
+! Added support for 'scope' attribute on tables.
 - Color keywords are now case insensitive.  Thanks Yzmir Ramirez
   <yramirez-htmlpurifier@adicio.com> for reporting.
 - Explicitly initialize anonModule variable to null.

docs/dev-progress.html

@@ -255,7 +255,7 @@ Mozilla on inside and needs -moz-outline, no IE support.</td></tr>
 <tr class="feature"><td>axis</td><td>TD, TH</td><td>W3C only: No browser implementation</td></tr>
 <tr class="feature"><td>char</td><td>COL, COLGROUP, TBODY, TD, TFOOT, TH, THEAD, TR</td><td>W3C only: No browser implementation</td></tr>
 <tr class="feature"><td>headers</td><td>TD, TH</td><td>W3C only: No browser implementation</td></tr>
-<tr class="feature"><td>scope</td><td>TD, TH</td><td>W3C only: No browser implementation</td></tr>
+<tr class="impl-yes"><td>scope</td><td>TD, TH</td><td>W3C only: No browser implementation</td></tr>
 </tbody>
 
 <tbody class="impl-yes">

library/HTMLPurifier/HTMLModule/Tables.php

@@ -37,6 +37,9 @@ class HTMLPurifier_HTMLModule_Tables extends HTMLPurifier_HTMLModule
                 'abbr'    => 'Text',
                 'colspan' => 'Number',
                 'rowspan' => 'Number',
+                // Apparently, as of HTML5 this attribute only applies
+                // to 'th' elements.
+                'scope'   => 'Enum#row,col,rowgroup,colgroup',
             ),
             $cell_align
         );