Implement type checking of list literals (issue 220).

tests/language/src/CanonicalConstTest.dart

Index: tests/language/src/CanonicalConstTest.dart
===================================================================
--- tests/language/src/CanonicalConstTest.dart	(revision 1805)
+++ tests/language/src/CanonicalConstTest.dart	(working copy)
@@ -25,7 +25,7 @@
     Expect.isTrue(const [2,1] !== const[1,2]);
     Expect.isTrue(const <int>[1,2] === const <int>[1,2]);
     Expect.isTrue(const <Object>[1,2] === const <Object>[1,2]);
-    Expect.isTrue(const <int>[1,2] !== const <double>[1,2]);
+    Expect.isTrue(const <int>[1,2] !== const <double>[1.0,2.0]);
     Expect.isTrue(const {"a":1, "b":2} === const {"a":1, "b":2});
     Expect.isTrue(const {"a":1, "b":2} !== const {"a":2, "b":2});
   }