vsync in linux can't be set
sdlayer_checkvsync does some magic to determine if vsync is locked. Later it prevents
videoSetVsync from change vsync options at all. However if i remove first check with
vsync_unsupported i can have tear-free image.
I suspect that
SDL_GL_GetSwapInterval reports either "adaptive sync" or "no sync" and this most likely breaks
sdlayer_checkvsync magic and disable vsync switching at all.