This correctly sets presentation modes for vsync, both at startup and at runtime via
a `setOptions` request.
Note: There may still be platforms where setting vsync is not enough, and a frame rate
limiter is needed to achieve proper synchronization. This is tracked in hexops/mach#444
and not fixed by this change.
Fixeshexops/mach#307
Signed-off-by: Stephen Gutekanst <stephen@hexops.com>
