bug#19798: 24.4; eww-mode error in process sentinel 'Invalid date' when receiving a valid date

[Matthew Carter <m@ahungry.com>]

When running eww-mode and visiting a site using a cookie expiration date
set to "Mon, 06 Mar 2130 20:55:03 GMT" eww-mode will fail to load
subsequent URLs on the domain (in this case http://ahungry.com) and
instead simply print the following message in the echo area:

error in process sentinel: Invalid date: Mon, 06 Mar 2130 20:55:03 GMT

According to Wikipedia and other sources I can find online regarding the
HTTP cookie expires field, this date format is valid
(https://en.wikipedia.org/wiki/HTTP_cookie) and should not be causing 
an error in the process sentinel (and even if some site sent an invalid
date, I don't think it should halt further site interaction, but either
ignore the invalid date, or ignore the cookie).

Steps to reproduce under emacs -Q:

eww
ahungry.com
RET
TAB
TAB
RET

You'll then see the error pop up (instead of visiting the Blog link on
the site).

-- 
Matthew Carter (m@ahungry.com)
http://ahungry.com