sys/sdl_glimp: allow r_swapInterval greater than 1, check for errors, fix #495
sys/sdl_glimp: allow r_swapInterval greater than 1, check for errors, fix #495

Allow r_swapInterval greater than 1 (and smaller than -1), fix #495
also fallback to generic sync on adaptive sync unavailability.

DaemonEngine/Daemon,DaemonEngine/Daemon,DaemonEngine/Daemon,DaemonEngine/Daemon