Use super rather than render_all in single block render classes.

lib/liquid/htmltags.rb

@@ -55,7 +55,7 @@ module Liquid
 
           col += 1
 
-          result << "<td class=\"col#{col}\">" << render_all(@nodelist, context) << '</td>'
+          result << "<td class=\"col#{col}\">" << super << '</td>'
 
           if col == cols and (index != length - 1)
             col  = 0

lib/liquid/tags/ifchanged.rb

@@ -4,7 +4,7 @@ module Liquid
     def render(context)
       context.stack do
 
-        output = render_all(@nodelist, context)
+        output = super
 
         if output != context.registers[:ifchanged]
           context.registers[:ifchanged] = output