fixes #221, initial sync*, async, async* implementation

test/codegen/expect/syncstar_syntax.txt

Index: test/codegen/expect/syncstar_syntax.txt
diff --git a/test/codegen/expect/syncstar_syntax.txt b/test/codegen/expect/syncstar_syntax.txt
index 5288ceb0b0d9d22652b8785896a5408649ed9fde..344be2d11d1143ee510d71987d681980ee23acdf 100644
--- a/test/codegen/expect/syncstar_syntax.txt
+++ b/test/codegen/expect/syncstar_syntax.txt
@@ -1,5 +1,8 @@
 // Messages from compiling syncstar_syntax.dart
-info: [InferredTypeLiteral] [2, 3] has inferred type Iterable<int> (test/codegen/syncstar_syntax.dart, line 7, col 10)
-info: [InferredTypeLiteral] [2, 3] has inferred type Iterable<int> (test/codegen/syncstar_syntax.dart, line 13, col 12)
-info: [InferredTypeLiteral] [2, 3] has inferred type Iterable<int> (test/codegen/syncstar_syntax.dart, line 18, col 12)
-info: [InferredTypeLiteral] [2, 3] has inferred type Iterable<int> (test/codegen/syncstar_syntax.dart, line 25, col 12)
+info: [DynamicCast] expected (dynamic) will need runtime check to cast to type String (package:expect/expect.dart, line 97, col 51)
+info: [DynamicCast] actual (dynamic) will need runtime check to cast to type String (package:expect/expect.dart, line 97, col 61)
+info: [DynamicInvoke] check(e) requires dynamic invoke (package:expect/expect.dart, line 372, col 14)
+info: [InferredTypeLiteral] [2, 3] has inferred type Iterable<int> (test/codegen/syncstar_syntax.dart, line 9, col 10)
+info: [InferredTypeLiteral] [2, 3] has inferred type Iterable<int> (test/codegen/syncstar_syntax.dart, line 15, col 12)
+info: [InferredTypeLiteral] [2, 3] has inferred type Iterable<int> (test/codegen/syncstar_syntax.dart, line 20, col 12)
+info: [InferredTypeLiteral] [2, 3] has inferred type Iterable<int> (test/codegen/syncstar_syntax.dart, line 27, col 12)