apache-httpd: Create runtime dir for version 2.4.

By default the path is determined related to ServerRoot. Unfortunately
ServerRoot is pointing to the Nix store and the web server can't write to it.

We now create a directory called "runtime" withen the stateDir and point
DefaultRuntimeDir to it.

For more information on the DefaultRuntimeDir directive, please see:

http://httpd.apache.org/docs/2.4/mod/core.html#defaultruntimedir



Signed-off-by: aszlig <aszlig@redmoonstudios.org>