.htaccess files: support Apache 2.4+ syntax

.htaccess files: support Apache 2.4+ syntax

If `mod_version` is enabled, the previous syntax will apply for Apache <2.4.
If not, the new syntax is used by default.

Fixes #676

`mod_version` identifier is `version_module` across all Apache versions. See:

  * https://httpd.apache.org/docs/current/mod/mod_version.html
  * https://httpd.apache.org/docs/2.2/mod/mod_version.html
  * https://serverfault.com/questions/733910/how-do-i-load-mod-version-only-if-it-isnt-built-in-to-apache

Note that version_module comes built-in with Debian (and derivatives) Apache2 packages, see https://wiki.debian.org/Apache/PackagingFor24