Support blockquote

RDoc::Markup::BlockQuote is supported by RDoc::Markdown, but not
RDoc::Markup yet and the syntax for it is not too.

This patch implements `>>>` as blockquote tentatively,

```
>>>
  foo
```

to

```
<blockquote><p>foo</p><blockquote>
```

Author: nobu

lib/rdoc/markup/parser.rb

@@ -9,8 +9,9 @@
 # RDoc::Markup::ToHTML.
 #
 # The parser only handles the block-level constructs Paragraph, List,
-# ListItem, Heading, Verbatim, BlankLine and Rule.  Inline markup such as
-# <tt>\+blah\+</tt> is handled separately by RDoc::Markup::AttributeManager.
+# ListItem, Heading, Verbatim, BlankLine, Rule and BlockQuote.
+# Inline markup such as <tt>\+blah\+</tt> is handled separately by
+# RDoc::Markup::AttributeManager.
 #
 # To see what markup the Parser implements read RDoc.  To see how to use
 # RDoc markup to format text in your program read RDoc::Markup.
@@ -381,6 +382,17 @@ def parse parent, indent = 0
       when :TEXT then
         unget
         parse_text parent, indent
+      when :BLOCKQUOTE then
+        type, _, column = get
+        if type == :NEWLINE
+          type, _, column = get
+        end
+        unget if type
+        bq = RDoc::Markup::BlockQuote.new
+        p :blockquote_start => [data, column] if @debug
+        parse bq, column
+        p :blockquote_end => indent if @debug
+        parent << bq
       when *LIST_TOKENS then
         unget
         parent << build_list(indent)
@@ -504,6 +516,9 @@ def tokenize input
                  # text:: followed by spaces or end of line => :NOTE
                  when @s.scan(/(.*?)::( +|\r?$)/) then
                    [:NOTE, @s[1], *token_pos(pos)]
+                 # >>> followed by end of line => :BLOCKQUOTE
+                 when @s.scan(/>>> *(\w+)?$/) then
+                   [:BLOCKQUOTE, @s[1], *token_pos(pos)]
                  # anything else: :TEXT
                  else @s.scan(/(.*?)(  )?\r?$/)
                    token = [:TEXT, @s[1], *token_pos(pos)]

test/test_rdoc_markup_parser.rb

@@ -1045,6 +1045,41 @@ def test_parse_whitespace
     assert_equal expected, @RMP.parse("  1\n   2\n\n    3").parts
   end
 
+  def test_parse_block_quote
+    expected = [
+      @RM::BlockQuote.new(@RM::Paragraph.new("foo"))
+    ]
+    assert_equal expected, @RMP.parse(<<-DOC).parts
+>>>
+  foo
+    DOC
+
+    expected = [
+      @RM::BlockQuote.new(@RM::Paragraph.new("foo"),
+                          @RM::Verbatim.new("code\n"),
+                          @RM::Paragraph.new("bar"))
+    ]
+    assert_equal expected, @RMP.parse(<<-DOC).parts
+>>>
+  foo
+    code
+  bar
+    DOC
+
+    expected = [
+      @RM::BlockQuote.new(@RM::Paragraph.new("foo"),
+                          @RM::BlockQuote.new(@RM::Paragraph.new("bar")),
+                          @RM::Paragraph.new("zot"))
+    ]
+    assert_equal expected, @RMP.parse(<<-DOC).parts
+>>>
+  foo
+  >>>
+    bar
+  zot
+    DOC
+  end
+
   def test_peek_token
     parser = util_parser