Initial support for FreeBSD platform:
- VnswInterfaceListener reimplemented for Linux and FreeBSD

Change-Id: I0e1dcf9f8cf1e5bd0f06b98365eff9a67d7c36f2
Authors: Grzegorz Bernacki, Michał Dubiel, Dominik Ermel
Merge "Initial support for FreeBSD platform: - VnswInterfaceListener reimplemented for Linux and FreeBSD"