Fix handling of "usemap" attribute (#1488472)

CHANGELOG

@@ -1,6 +1,7 @@
 CHANGELOG Roundcube Webmail
 ===========================
 
+- Fix handling of "usemap" attribute (#1488472)
 - Fix handling of some HTML tags e.g. IMG (#1488471)
 - Use similar language as a fallback for plugin localization (#1488401)
 - Fix issue where signature wasn't re-added on draft compose (#1488322)

program/lib/washtml.php

@@ -101,7 +101,7 @@ class washtml
     'cellpadding', 'valign', 'bgcolor', 'color', 'border', 'bordercolorlight',
     'bordercolordark', 'face', 'marginwidth', 'marginheight', 'axis', 'border',
     'abbr', 'char', 'charoff', 'clear', 'compact', 'coords', 'vspace', 'hspace',
-    'cellborder', 'size', 'lang', 'dir',
+    'cellborder', 'size', 'lang', 'dir', 'usemap',
     // attributes of form elements
     'type', 'rows', 'cols', 'disabled', 'readonly', 'checked', 'multiple', 'value'
   );