Log Message:
Changes with Apache 2.4.27

  *) COMPATIBILITY: mod_lua: Remove the undocumented exported 'apr_table'
     global variable when using Lua 5.2 or later. This was exported as a
     side effect from luaL_register, which is no longer supported as of
     Lua 5.2 which deprecates pollution of the global namespace.

  *) COMPATIBILITY: mod_http2: Disable and give warning when using Prefork.
     The server will continue to run, but HTTP/2 will no longer be negotiated.

  *) COMPATIBILITY: mod_proxy_fcgi: Revert to 2.4.20 FCGI behavior for the
     default ProxyFCGIBackendType, fixing a regression with PHP-FPM.

  *) mod_lua: Improve compatibility with Lua 5.1, 5.2 and 5.3.

  *) mod_http2: Simplify ready queue, less memory and better performance. Update
     mod_http2 version to 1.10.7.

  *) Allow single-char field names inadvertently disallowed in 2.4.25.

  *) htpasswd / htdigest: Do not apply the strict permissions of the temporary
     passwd file to a possibly existing passwd file.

  *) core: Avoid duplicate HEAD in Allow header.
     This is a regression in 2.4.24 (unreleased), 2.4.25 and 2.4.26.