normalize

# File lib/rexml/text.rb, line 372
    def Text::normalize( input, doctype=nil, entity_filter=nil )
      copy = input.to_s
      # Doing it like this rather than in a loop improves the speed
      #copy = copy.gsub( EREFERENCE, '&' )
      copy = copy.gsub( "&", "&" )
      if doctype
        # Replace all ampersands that aren't part of an entity
        doctype.entities.each_value do |entity|
          copy = copy.gsub( entity.value,
            "&#{entity.name};" ) if entity.value and
              not( entity_filter and entity_filter.include?(entity.name) )
        end
      else
        # Replace all ampersands that aren't part of an entity
        DocType::DEFAULT_ENTITIES.each_value do |entity|
          copy = copy.gsub(entity.value, "&#{entity.name};" )
        end
      end
      copy
    end