[New port] games/quake4

id Software has released Linux binaries for Quake 4! Hooray!
They seem to work on FreeBSD as well (worked on my machine,
about 5 FPS ;-)).

There isn't a port for it at the moment, so I've made one.
I don't feel like maintaining it, because I can't really
test it on my machine.

The port isn't complete; There isn't a switch to install
dedicated only (wouldn't be hard though) and I guess we
shouldn't be able to build packages from it.

Have fun! :-)

• Renamed it to games/linux-quake4 to stay consistent with other quake ports.

PR: ports/87764
Submitted by: Ed Schouten <ed@fxq.nl>