GitLab

This fixes make distcheck and the distribution tarballs, those
were previously lacking this header which caused builds to fail.

This will build icecast using Gitlab CI on the Xiph Gitlab with a
Docker image of Alpine Linux.

Changelog and docs still need updating.

404 is the expected result

This adds support to read metadata from Ogg/Opus streams:
 * Original sample rate from OpusHead,
 * number of channels from OpusHead,
 * Tags from OpusTags.

This adds spaces into the strings such as "nomatch" (-> "no match")
as returned by auth_result2str(). This is to improve readability of
resulting logfiles by most uses.