Fix HTTP links in URI docs.

lib/dartdoc/markdown.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// Parses text in a markdown-like format and renders to HTML.
 #library('markdown');
 
 #source('ast.dart');
 #source('block_parser.dart');
 #source('html_renderer.dart');
@@ skipping 39 matching lines @@
     final quote = @'"[^"]+"';    // Title in "double quotes".
     final apos = @"'[^']+'";     // Title in 'single quotes'.
     final paren = @"\([^)]+\)";  // Title in (parentheses).
     final pattern = new RegExp(
         '$indent$id:\\s+(\\S+)\\s*($quote|$apos|$paren|)\\s*\$');
 
     for (int i = 0; i < lines.length; i++) {
       final match = pattern.firstMatch(lines[i]);
       if (match != null) {
         // Parse the link.
-        final id = match[1];
-        final url = match[2];
+        var id = match[1];
+        var url = match[2];
         var title = match[3];
 
         if (title == '') {
           // No title.
           title = null;
         } else {
           // Remove "", '', or ().
           title = title.substring(1, title.length - 1);
         }
 
+        // References are case-insensitive.
+        id = id.toLowerCase();
+
         refLinks[id] = new Link(id, url, title);
 
         // Remove it from the output. We replace it with a blank line which will
         // get consumed by later processing.
         lines[i] = '';
       }
     }
   }
 
   /// Parse the given [lines] of markdown to a series of AST nodes.
@@ skipping 20 matching lines @@
   /// `<em>this <strong>is</strong> a</em> <code>markdown</code>`.
   List<Node> parseInline(String text) => new InlineParser(text, this).parse();
 }
 
 class Link {
   final String id;
   final String url;
   final String title;
   Link(this.id, this.url, this.title);
 }