pvr: fix channel switch for addons using other stream
CGUISliderControl: only switch between selectors on <Enter> if there are more than one
Read CD audio USB drive bug fixed

libcdio seems to allow read no more than about 10 audio sectors at once when CD audio device is connected via USB.
This patch makes XBMC read small number of sectors if default one fails. It uses more CPU but allows to use USB CD devices.
Tested on GNU/Linux x86 and RPi. (On Rpi OMXPlayer does not play CD, but I can rip tracks).
Fix undefined reference caused by wrong detection of gcc builtin atomic functions.
Fix color index overflow by reuse existed color in the vector. Fix #14293
avoid detect folder.jpg under 'add' item.
Check exists before listing dir, to avoid produce error log, fix #14210