Commits below update xawtv; fife engine and unknown horizons

Version in the tree no longer works with current kernel as it doesn't support v4l2. So updated as I needed a quick check if a webcam worked. 

In doing so cleaned up the ebuild and checked use-flags and dependencies, but can't do much testing beyond saying that it works well enough for me. 

Fixes gentoo bug https://bugs.gentoo.org/show_bug.cgi?id=358013

--- edit ---

Github unfortunately mergest requests. Second set of commits is to make the Fife Game Engine work on Funtoo. Based on an ebuild in the gamerlay overlay with fixes to cope with the presence of both Python2 and Python3

-- edit --

New commit to add is an ebuild for Unknown Horizons based on one in the gamerlay overlay but fixed to install in the correct locations. Works for me

-- edit --

Running unknown horizons revealed a memory leak in the fife-engine that flooded the terminal. Attached commit fixes that leak; based on upstream commit 3949.