• Enhanced checks for wildcard domain names in certificate coverage.
• ACME authorizations and certificate requests only done for minimal set of domain names,
  e.g. domain covered by a wildcard are left out. LE CA requires this.
• First successful wildcard certificate signup in test suite
• Old and long deprecated configuration directives "ManagedDomain(s)" removed.
• Challenge type 'tls-sni-01' removed as it has been disabled by Let's Encrypt.
• When the ACME server threw its challenges at us, we selected the first among the
  configured/supported ones and ran that. When it failed, the whole authorization
  failed until the retry kicked in. Now, on a failed challenge startup, we look for the
  next possible challenge type and try that.
  This allows for challenge types that are configured and maybe supported in general,
  but do not work for all domains. E.g. when we add DNS challenge support, that type
  may only work for a subset of the domains.
  Instead of putting the burden on the user to configured the MDomains individually
  correct, the DNS challenge setup can just return APR_ENOTIMPL and another challenge
  type is used (if available).
• configure updated to better work with non-standard curl library locations.