accela: remove now-unused mutex
remove undefined member function from class
replace incorrect interpolation with nearest neighbor
don't load spline config twice
add SDK_LIBEVDEV to enable users to select libevdev path.
vjoy: Fix POV hat state

POV hat key was always stuck in one position, confusing certain games.

Reported-by: ASQ_Dak
Fix-by: Rickard Öberg
Tested-by: no one at all!
Merge pull request #30 from okdshin/enable_to_select_libevdev_path

add SDK_LIBEVDEV to enable users to select libevdev path.
Update README.md