security/gssproxy: Add new Port

GSS Proxy allows processes to perform GSSAPI operations, such as
Kerberos authentication, through a privileged daemon. This separates
credential handling from the application and lets services access
keytabs and credential caches without holding the privileges directly.

WWW: https://github.com/gssapi/gssproxy

Sponsored by: Netzkommune GmbH

Required for: FreeIPA server port