rename singleton_class to single_class and misc

was clashing with real ruby method name
also many superclass mismatch fixes
some misc

lib/ruby/method_statement.rb

@@ -39,7 +39,7 @@ module Ruby
 
     def to_s(depth = 0)
       arg_str = @args.collect{|a| a.to_s}.join(', ')
-      at_depth(depth , "def #{name}(#{arg_str})" , @body.to_s(depth + 1) , "end")
+      at_depth(depth , "def #{name}(#{arg_str})\n #{@body.to_s(1)}\nend")
     end
 
   end