Following RFC 6265 Section 5.1.1.5, ensure that the minimum
year for which an Expires value is valid and can be included in
the cookie's string, is 1601 instead of the Epoch year 1970.

A detailed specification for parsing the Expiry field is at:
https://tools.ietf.org/html/rfc6265#section-5.2.1

I stumbled across this bug due to this StackOverflow answer
that recommends setting the Expiry to the Epoch:
http://stackoverflow.com/a/5285982

Fixes #17632

Change-Id: I3c1bdf821d369320334a5dc1e4bf22783cbfe9fc
Reviewed-on: https://go-review.googlesource.com/32142Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>