Sync with latest HTML5lib and latest Maruku

vendor/plugins/HTML5lib/lib/html5/serializer/xhtmlserializer.rb

@@ -0,0 +1,20 @@
+require 'html5/serializer/htmlserializer'
+
+module HTML5
+
+  class XHTMLSerializer < HTMLSerializer
+    DEFAULTS = {
+      :quote_attr_values => true,
+      :minimize_boolean_attributes => false,
+      :use_trailing_solidus => true,
+      :escape_lt_in_attrs => true,
+      :omit_optional_tags => false,
+      :escape_rcdata => true
+    }
+
+    def initialize(options={})
+      super(DEFAULTS.clone.update(options))
+    end
+  end
+
+end