Remove `Cohttp_mirage` libraries, which have now moved to
mirage/mirage-http-unix and mirage/mirage-http-xen.

The previous libraries were being inconsistently compiled across
Unix and Xen, and this split is required is disambiguate them.
See mirage/mirage#161 for more information.
httponly cookie attribute
fix cookie parsing to allow = in values
update tests for case where '=' is in cookie value
Merge branch 'http_only' of git://github.com/rgrinberg/ocaml-cohttp
Merge branch 'cookie_fix' of git://github.com/rgrinberg/ocaml-cohttp
Add @rgrinberg to the authors, and sync CHANGES