fix(typings): repair broken typechecks

We had the typechecker disabled by accident, and many problems snuck in

Fixes #4507

Closes #4508

modules/angular2/src/core/facade/lang.ts

@@ -58,7 +58,7 @@ export function CONST_EXPR<T>(expr: T): T {
   return expr;
 }
 
-export function CONST(): ClassDecorator {
+export function CONST(): ClassDecorator & PropertyDecorator {
   return (target) => target;
 }
 

modules/angular2/src/core/util/decorators.ts

@@ -18,7 +18,13 @@ export interface ClassDefinition {
    *
    * See {@link Class} for example of usage.
    */
-  constructor: (Function | any[]);
+  constructor: Function | any[];
+
+  /**
+   * Other methods on the class. Note that values should have type 'Function' but TS requires
+   * all properties to have a narrower type than the index signature.
+   */
+  [x: string]: Type | Function | any[];
 }
 
 /**

modules/angular2/test/core/forms/directives_spec.ts

@@ -93,7 +93,7 @@ export function main() {
         });
 
         it("should throw when more than one custom accessor is provided", () => {
-          var customAccessor = new SpyValueAccessor();
+          var customAccessor: ControlValueAccessor = <any>new SpyValueAccessor();
           expect(() => selectValueAccessor(dir, [customAccessor, customAccessor])).toThrowError();
         });
       });

modules/angular2/test/core/forms/model_spec.ts

@@ -156,7 +156,7 @@ export function main() {
               {"one": new Control("111"), "nested": new ControlGroup({"two": new Control("222")})});
           expect(g.value).toEqual({"one": "111", "nested": {"two": "222"}});
 
-          g.controls["nested"].controls["two"].updateValue("333");
+          (<Control>(g.controls["nested"].find("two"))).updateValue("333");
 
           expect(g.value).toEqual({"one": "111", "nested": {"two": "333"}});
         });

modules/angular2/test/core/zone/ng_zone_spec.ts

@@ -11,8 +11,7 @@ import {
   xit,
   Log,
   isInInnerZone,
-  browserDetection,
-  TIMEOUT_INTERVAL_FOR_SLOW_BROWSERS
+  browserDetection
 } from 'angular2/test_lib';
 
 import {PromiseCompleter, PromiseWrapper, TimerWrapper} from 'angular2/src/core/facade/async';