Premise: When pose bones are selected, applying a pose library should only affect the selected bones. This commit fixes a bug where the pose was also applied when there was no overlap between the selected bones and the bones in the pose. For example, applying a pose which contains only keyframes for the left hand, while only right-hand bones are selected, would apply the pose to the left hand anyway. The code is now also slightly more efficient; the removed 'selcount' counter was only used as a binary (i.e. zero or non-zero). It's now stored as a bitflag instead.