add https support to chttpd
add https support to chttpd

Bigcouch nodes don't support direct https connection right now and you
need to use another level on top of the proxy to support it (tunnel or
such). This patch backport https support from couchdb.

https options are set in [chttps] section to not ovveride [ssl] section
from couchdb. Options supported are:

- port
- cert_file
- key_file
- password (use for the cety file)
- verify_ssl_certificates (default false) , validation per certificate
- cacert_file : path to file containing PEM encoded CA certificates
- verify_fun , The verification fun (optionnal) if not specidied, the
  default verification fun will be used.
- ssl_certificate_max_depth (default to 1)

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