[Openid-specs-mobile-profile] Issue #188: Behaviour update with simultaneous polling requests (openid/mobile)

[naillery]

New issue 188: Behaviour update with simultaneous polling requests
https://bitbucket.org/openid/mobile/issues/188/behaviour-update-with-simultaneous-polling

Nicolas Aillery:

‌

```
The first polling request must be favored over the newest ones. The newest ones must be responded with an error
-
The Client sent simultaneous requests to the User Questioning Polling Endpoint for the same <spanx style="verb">question_id</spanx>. This error is responded to oldest requests. The last request is processed normally.
+
The Client sent simultaneous requests to the User Questioning Polling Endpoint for the same <spanx style="verb">question_id</spanx>. This error is responded to newer requests. The oldest request is processed normally.
```

‌