strongswan 5.2.0

As noted in the commit message, `--enable-tools` was replaced by the `--enable-pki` and `--enable-scepclient` options. `--enable-swanctl` enables a new [configuration and control interface](https://wiki.strongswan.org/projects/strongswan/wiki/swanctl) that can be used instead of the old ipsec.conf-based one (since they are not mutually exclusive both are currently enabled).