PHP - oauth_callback is not used in from_consumer_and_token

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What steps will reproduce the problem?
1. Create an instance of OAuthConsumer WITH a callback_url
2. Create an instance of OAuthRequest using from_consumer_and_token

What is the expected output? What do you see instead?
I expect that my previous set callback_url is used in the request, but nothing 
is done with the callback_url; I have to set it manually as part of $parameters 
in from_consumer_and_token.

Please use labels and text to provide additional information.
The callback_url in OAuthConsumer is set to a non-declared property, which 
results in a E_STRICT warning. Declaring this property seems like an easy fix 
in addition to the issue above.

Original issue reported on code.google.com by [email protected] on 28 Dec 2012 at 9:16