Only allow secure origins to be able to write cookies with the
'secure' flag set. This reduces the risk of non-secure origins
to influence the state of secure origins. This implements IETF
Internet-Draft draft-ietf-httpbis-cookie-alone-01 which updates
RFC6265.
Closes#2956
Reviewed-by: Daniel Stenberg <daniel@haxx.se>
RFC 6265 section 4.2.1 does not set restrictions on cookie names.
This is a follow-up to commit 7f7fcd0.
Also explicitly check proper syntax of cookie name/value pair.
New test 1155 checks that cookie names are not reserved words.
Reported-By: anshnd at github
Fixes#2564Closes#2566
