Most basic support for $::osfamily = 'RedHat'

The following three minimal commits add the most basic support for RedHat.

I am testing on CentOS 6.5. I will develop this further.

The SSL stuff will be more different, because on CentOS, openldap is being linked against NSS, using certutil for certificiate management. That means, in /etc/openldap/certs there is a cert8.db and so on, nothing is like openssl users expect. That's why I am leaving this out for now and will add a larger patch later.