httpd 2.2.25

httpd information in httpd.rb is outdated.
So, the following command failed.

```
$ brew install httpd
==> Downloading http://www.apache.org/dist/httpd/httpd-2.2.23.tar.bz2

curl: (22) The requested URL returned error: 404
Error: Download failed: http://www.apache.org/dist/httpd/httpd-2.2.23.tar.bz2
```

I fixed this problem by this pull request.