[http-state] Max-Age

[Adam Barth <[e-mail]>]

The test suite has revealed that the Max-Age cookie attribute is supported by

Firefox
Safari
Chrome
Opera
CURL

and ignored by

Internet Explorer

We have two decisions to make:

1) Should we include Max-Age in the user agent conformance section?

It seems clear that Max-Age has wide enough deployment that new user
agent implementors will want to include support.  Therefore, I think
we should include Max-Age in the user agent conformance section.

2) Should we include Max-Age in the server conformance section?

I also think that we should include Max-Age in the server conformance
section because Max-Age has broad enough implementation among user
agents (i.e., all but IE) and is sufficiently incrementally deployable
that I think it's possible that including it in the spec will cause
Internet Explorer to adopt the attribute, which would improve
interoperability.

Of course, we should also include Expires, which is supported by every
major implementation.  We might also want to include a note that at
the time of this writing, the Expires attribute has been implemented
by more user agents.

Adam