new port: multimedia/nxtvepg (electronic tv programme guide, bktr)

This is a new port for nxtvepg, an electronic tv programme
guide that extracts its information from special teletext
signals.

The programming will need a working tv tuner card that is
supported by the bktr(4) driver.

PR: ports/46847
Submitted by: Simon Barner <barner@in.tum.de>