Documentation for migration from C2DM needs updating for Android 5.0

```
The documentation for how to migrate from C2DM to GCM, at 
https://developer.android.com/google/gcm/c2dm.html#client, gives code that that 
uses an implicit intent to start a service, which is no longer allowed in 
Android 5.0.


```

Original issue reported on code.google.com by `mohamed....@gmail.com` on 16 Nov 2014 at 5:33
