Fix a bug that SAX2 parser doesn't expand the predefined entities for "characters" (#168)

## Why?

SAX2 parser expand user-defined entity references and character
references but doesn't expand predefined entity references.

## Change
- text_unnormalized.rb
```
require 'rexml/document'
require 'rexml/parsers/sax2parser'
require 'rexml/parsers/pullparser'
require 'rexml/parsers/streamparser'

xml = <<EOS
<root>
  <A>&lt;P&gt;&#13; &lt;I&gt; &lt;B&gt; Text &lt;/B&gt;  &lt;/I&gt;</A>
</root>
EOS

class Listener
  def method_missing(name, *args)
    p [name, *args]
  end
end

puts "REXML(DOM)"
REXML::Document.new(xml).elements.each("/root/A") {|element| puts element.text}

puts ""
puts "REXML(Pull)"
parser = REXML::Parsers::PullParser.new(xml)
while parser.has_next?
    res = parser.pull
    p res
end

puts ""
puts "REXML(Stream)"
parser = REXML::Parsers::StreamParser.new(xml, Listener.new).parse

puts ""
puts "REXML(SAX)"
parser = REXML::Parsers::SAX2Parser.new(xml)
parser.listen(Listener.new)
parser.parse
```

## Before (master)
```
$ ruby text_unnormalized.rb
REXML(DOM)
 <I> <B> Text </B>  </I>

REXML(Pull)
start_element: ["root", {}]
text: ["\n  ", "\n  "]
start_element: ["A", {}]
text: ["&lt;P&gt;&#13; &lt;I&gt; &lt;B&gt; Text &lt;/B&gt;  &lt;/I&gt;", "<P>\r <I> <B> Text </B>  </I>"]
end_element: ["A"]
text: ["\n", "\n"]
end_element: ["root"]
end_document: []

REXML(Stream)
[:tag_start, "root", {}]
[:text, "\n  "]
[:tag_start, "A", {}]
[:text, "<P>\r <I> <B> Text </B>  </I>"]
[:tag_end, "A"]
[:text, "\n"]
[:tag_end, "root"]

REXML(SAX)
[:start_document]
[:start_element, nil, "root", "root", {}]
[:progress, 6]
[:characters, "\n  "]
[:progress, 9]
[:start_element, nil, "A", "A", {}]
[:progress, 12]
[:characters, "&lt;P&gt;\r &lt;I&gt; &lt;B&gt; Text &lt;/B&gt;  &lt;/I&gt;"] #<= This
[:progress, 74]
[:end_element, nil, "A", "A"]
[:progress, 78]
[:characters, "\n"]
[:progress, 79]
[:end_element, nil, "root", "root"]
[:progress, 86]
[:end_document]
```

## After(This PR)
```
$ ruby text_unnormalized.rb
REXML(SAX)
[:start_document]
[:start_element, nil, "root", "root", {}]
[:progress, 6]
[:characters, "\n  "]
[:progress, 9]
[:start_element, nil, "A", "A", {}]
[:progress, 12]
[:characters, "<P>\r <I> <B> Text </B>  </I>"]
[:progress, 74]
[:end_element, nil, "A", "A"]
[:progress, 78]
[:characters, "\n"]
[:progress, 79]
[:end_element, nil, "root", "root"]
[:progress, 86]
[:end_document]
```

Author: naitoh

lib/rexml/parsers/sax2parser.rb

@@ -157,25 +157,8 @@ def parse
               end
             end
           when :text
-            #normalized = @parser.normalize( event[1] )
-            #handle( :characters, normalized )
-            copy = event[1].clone
-
-            esub = proc { |match|
-              if @entities.has_key?($1)
-                @entities[$1].gsub(Text::REFERENCE, &esub)
-              else
-                match
-              end
-            }
-
-            copy.gsub!( Text::REFERENCE, &esub )
-            copy.gsub!( Text::NUMERICENTITY ) {|m|
-              m=$1
-              m = "0#{m}" if m[0] == ?x
-              [Integer(m)].pack('U*')
-            }
-            handle( :characters, copy )
+            unnormalized = @parser.unnormalize( event[1], @entities )
+            handle( :characters, unnormalized )
           when :entitydecl
             handle_entitydecl( event )
           when :processing_instruction, :comment, :attlistdecl,

lib/rexml/parsers/streamparser.rb

@@ -36,8 +36,8 @@ def parse
             @listener.tag_end( event[1] )
             @tag_stack.pop
           when :text
-            normalized = @parser.unnormalize( event[1] )
-            @listener.text( normalized )
+            unnormalized = @parser.unnormalize( event[1] )
+            @listener.text( unnormalized )
           when :processing_instruction
             @listener.instruction( *event[1,2] )
           when :start_doctype

test/test_pullparser.rb

@@ -82,6 +82,22 @@ def test_character_references
       assert_equal("B", events['b'])
     end
 
+    def test_text_entity_references
+      source = '<root><a>&lt;P&gt; &lt;I&gt; &lt;B&gt; Text &lt;/B&gt;  &lt;/I&gt;</a></root>'
+      parser = REXML::Parsers::PullParser.new( source )
+
+      events = []
+      while parser.has_next?
+        event = parser.pull
+        case event.event_type
+        when :text
+          events << event[1]
+        end
+      end
+
+      assert_equal(["<P> <I> <B> Text </B>  </I>"], events)
+    end
+
     def test_text_content_with_line_breaks
       source = "<root><a>A</a><b>B\n</b><c>C\r\n</c></root>"
       parser = REXML::Parsers::PullParser.new( source )

test/test_sax.rb

@@ -31,6 +31,17 @@ def test_entity_replacement
       assert_equal '--1234--', results[1]
     end
 
+    def test_characters_predefined_entities
+      source = '<root><a>&lt;P&gt; &lt;I&gt; &lt;B&gt; Text &lt;/B&gt;  &lt;/I&gt;</a></root>'
+
+      sax = Parsers::SAX2Parser.new( source )
+      results = []
+      sax.listen(:characters) {|x| results << x }
+      sax.parse
+
+      assert_equal(["<P> <I> <B> Text </B>  </I>"], results)
+    end
+
     def test_sax2
       File.open(fixture_path("documentation.xml")) do |f|
         parser = Parsers::SAX2Parser.new( f )