Implement named constructors and resolving of redirecting constructors and super-initializers.

frog/leg/scanner/listener.dart

Index: frog/leg/scanner/listener.dart
diff --git a/frog/leg/scanner/listener.dart b/frog/leg/scanner/listener.dart
index 2a116d4e1120b1343535cf6ed5d8157028f92ed7..a5713751dac216e0a7e54aaeddc738910bd107d0 100644
--- a/frog/leg/scanner/listener.dart
+++ b/frog/leg/scanner/listener.dart
@@ -860,7 +860,8 @@ class NodeListener extends ElementListener {
     Statement body = popNode();
     NodeList initializers = popNode();
     NodeList formals = popNode();
-    Identifier name = popNode();
+    // The name can be an identifier or a send in case of named constructors.
+    Expression name = popNode();
     TypeAnnotation type = popNode();
     Modifiers modifiers = popNode();
     pushNode(new FunctionExpression(name, formals, body, type,