(fixes an incorrect behaviour when clicking on the white part of the slider)

- Use strlcpy()

Might be a better idea to implement strlcpy()

- Clean up

* Fix for some strange x drivers that return 8 bits screens as first answer when being requested a Truecolor class one

in any case (however unlikely we were to fall far it on Linux)

* Instead, use "screensaver,none" when trying to load the screensaver interface
* Same fix for onther interfaces loaded by libvlc

Fix #525 Fixes #525