Revert screensaver focus behaviour

The below change seems to have been pushed through to Frodo and I don't believe it's an appropriate default behaviour change or the best way to resolve the problem.

https://github.com/xbmc/xbmc/pull/1183

This is to help the small number of people using a single plasma screen, that still is vulnerable to burn-in, and who then use that same single box for other functions while XBMC is in the background.

I don't believe that number comes anywhere near the number of people using dual monitors and who rarely have XBMC focused while playing video and will learn that their OS screensaver will now kick in every time they take a step back and fail to give it focus.

The default behaviour should be reverted but to solve the plasma problem, for the half dozen people it will affect once in a blue moon, this behaviour should be an option or the default behaviour of XBMC is dependant on how many screens the system is using.

There appears to be an option (new?) to dim to 0% under the XBMC screensaver which may resolve this issue so there may be no need for a further solution let alone one so annoying for so many more people.