As clarified in https://tools.ietf.org/html/rfc7936 the IANA
registry only accepts case insensitive values for clarity's
sake but the actual tokens are case sensitive.

Some cookies are seen in the wild consisting of just a name, without
even a "=" char. This allows parsing them as if they were written
"foo=", that is with an empty value.

Commit amended to add a few more test cases.

Edited to add a test and use byte_size instead of size.

This will avoid issues with other people's build systems.