Add parser support for DoH configuration options

Add parser support for DoH configuration options

This commit adds stub parser support and tests for:
- an "http" global option for HTTP/2 endpoint configuration.
- command line options to set http or https port numbers by
  specifying -p http=PORT or -p https=PORT.  (NOTE: this change
  only affects syntax; specifying HTTP and HTTPS ports on the
  command line currently has no effect.)
- named.conf options "http-port" and "https-port"
- HTTPSPORT environment variable for use when running tests.