Move ActionView::Base#is_haml? to action_view_mods.rb.

lib/haml/helpers.rb

@@ -407,11 +407,3 @@ END
     include ActionViewExtensions if self.const_defined? "ActionViewExtensions"
   end
 end
-
-module ActionView
-  class Base # :nodoc:
-    def is_haml?
-      false
-    end
-  end
-end

lib/haml/helpers/action_view_mods.rb

@@ -1,6 +1,10 @@
 if defined?(ActionView) and not defined?(Merb::Plugins)
   module ActionView
     class Base # :nodoc:
+      def is_haml?
+        false
+      end
+
       def render_with_haml(*args, &block)
         return non_haml { render_without_haml(*args, &block) } if is_haml?
         render_without_haml(*args, &block)