[HttpFoundation] better fix for non-parseable Expires header date

It also fixes several phpdocs
[HttpFoundation] fix return types and handling of zero in Response
merged branch Tobion/expires-header (PR #6535)

This PR was merged into the 2.1 branch.

Commits
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10b01c9 [HttpFoundation] fix return types and handling of zero in Response
75952af [HttpFoundation] better fix for non-parseable Expires header date

Discussion
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[HttpFoundation] Response fixes

First commit is a better solution for #6471 and also fixes several phpdocs.
The second commit fixes the return types and handling of zero.

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by Tobion at 2013-01-02T21:16:25Z

@dlsniper cc