Swift 4.2.1 Release

Various Cookie fixes (#1706)

* Various Cookie fixes

- Add support for additional Set-Cookie formats that web servers can return
- Properly handle HTTP header parsing to extract values since values can contain colons
- Make sure to set cookies on redirect requests
- Use setValue instead of addValue when applying cookies to requests otherwise,
  Cookie header might contain: cookie1=value1,cookie1=value1; cookie2=value2
- New unit tests for cookie formats and redirect with Set-Cookie

(cherry picked from commit 97a93b5d4c1fca906254172896086183021ef374)

* Remove two-digit year cookie format support & unit test (fails on Ubuntu 14.04) (#1707)