Detect monkey patching and emit a deprecation warning.

This isn't comprehensive but it should be broad enough to ensure that most
people who would be affected by blocking monkey patching see a warning.
Covers the jasmine namespace as well as classes that are monkey patched by
zone.js.

Replacing globals (describe/it/etc) doesn't trigger a warning because they
belong to the user and are expected to be replaced.

spec/core/baseSpec.js

@@ -170,8 +170,15 @@ describe('base helpers', function() {
   });
 
   describe('debugLog', function() {
+    beforeEach(function() {
+      privateUnderTest.currentEnv_ = jasmine.createSpyObj('env', ['debugLog']);
+    });
+
+    afterEach(function() {
+      privateUnderTest.currentEnv_ = null;
+    });
+
     it("forwards to the current env's debugLog function", function() {
-      spyOn(jasmineUnderTest.getEnv(), 'debugLog');
       jasmineUnderTest.debugLog('a message');
       expect(jasmineUnderTest.getEnv().debugLog).toHaveBeenCalledWith(
         'a message'