Add compatibility for apache 2.4 out of the box

[endelwar]

Using .htaccess as is on Apache 2.4 make it halt with error 500 because Order directive is deprecated in favour of Require.
This patch checks existence of mod_authz_host module, available in Apache 2.3 and later and uses the right directive supported by Apache

[alrra]

@endelwar the solution won't work for both Apache v2.2.x and v2.4.x because Apache 2.2.x has the Allow, Deny, and Satisfy directives under the "same" module: mod_authz_host.c :(

• Apache v2.2.x docs
• Apache v2.4.x docs

Also relevant to this issue: http://httpd.apache.org/docs/trunk/upgrading.html#access

[endelwar]

@alrra yes, that's right, same module name, different functions :(
I've tested the mod_version presence on ubuntu 12.04, debian 6 and debian 7: it's statically compiled so it should be present in major distribution. We should get an httpd -M or apachectl -M from different installation (linux, osx, freebsd, windows) and different version to be 100% sure of this.

[endelwar]

Eventually we can check for mod_authz_core, that not exists in apache < 2.3

[alrra]

we can check for mod_authz_core

@endelwar yes, that seems to be a better solution as mod_authz_core has the "base" status, while mod_version has only the "extension" status.

Base
A module labeled as having "Base" status is compiled and loaded into the server by default, and is therefore normally available unless you have taken steps to remove the module from your configuration.

Extension
A module with "Extension" status is not normally compiled and loaded into the server. To enable the module and its functionality, you may need to change the server build configuration files and re-compile Apache.

---

# Apache < 2.3
<IfModule !mod_authz_core.c>
    Order allow,deny
    Deny from all
    Satisfy All
</IfModule>

# Apache ≥ 2.3
<IfModule mod_authz_core.c>
    Require all denied
</IfModule>           

Tested the above in Apache/2.2.24 and Apache/2.4.6.

---

@endelwar can you merge the commits into one and provide a more detail commit message ? Thanks!

[alrra]

@endelwar thanks!