Make the date parser accept invalid dates like
"Thu, 10 Dec 09 15:08:08 GMT-0700" which was observed in an email from eBay.
Per RFC, timezone must be either obs-zone (e.g. "GMT") or +/- with 4 digits.
The GMT+/-digits format is not permitted.
Bug 2367124
Backport of I59968274160aeadea70223208b463ee692660056
Change-Id: I3c80eee28d1dcf4c0c211f773a50de0f0839e4ad