*) mod_md: adding v2.4.8 with the following changes

  *) mod_md: adding v2.4.8 with the following changes
    - Added support for ACME External Account Binding (EAB).
      Use the new directive `MDExternalAccountBinding` to provide the
      server with the value for key identifier and hmac as provided by
      your CA.
      While working on some servers, EAB handling is not uniform
      across CAs. First tests with a Sectigo Certificate Manager in
      demo mode are successful. But ZeroSSL, for example, seems to
      regard EAB values as a one-time-use-only thing, which makes them
      fail if you create a seconde account or retry the creation of the
      first account with the same EAB.
    - The directive 'MDCertificateAuthority' now checks if its parameter
      is a http/https url or one of a set of known names. Those are
      'LetsEncrypt', 'LetsEncrypt-Test', 'Buypass' and 'Buypass-Test'
      for now and they are not case-sensitive.
      The default of LetsEncrypt is unchanged.
    - `MDContactEmail` can now be specified inside a `<MDomain dnsname>`
      section.
    - Treating 401 HTTP status codes for orders like 403, since some ACME
      servers seem to prefer that for accessing oders from other accounts.
    - When retrieving certificate chains, try to read the repsonse even
      if the HTTP Content-Type is unrecognized.
    - Fixed a bug that reset the error counter of a certificate renewal
      and prevented the increasing delays in further attempts.
    - Fixed the renewal process giving up every time on an already existing
      order with some invalid domains. Now, if such are seen in a previous
      order, a new order is created for a clean start over again.
      See <https://github.com/icing/mod_md/issues/268>
    - Fixed a mixup in md-status handler when static certificate files
      and renewal was configured at the same time.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1894610 13f79535-47bb-0310-9956-ffa450edef68