Many improvements for smooth audio playback when 'time' keyframes are used for time remapping.

- Added new Frame::ReverseAudio() helper method - for time keyframe support playing backwards audio
- Fixed math rounding error on time keyframe Resampler, to use the rounded source samples value
- Removed some unused args and Frame audio methods
- Reset FrameMapper resample context when non-adjacent frames are requested
- Correctly reverse Frame audio if a time keyframe is present, and reversing audio
- Rewrite Keyframe::IsIncreasing() function, to give accurate direction of time keyframes at any index (special logic to support first and last indexes)
- Fixed Keyframe unit tests - since logic has changed a bit
- Improved time mapping unit tests
- Replace many c-style casts with static_cast
- Added new sine.wav test file

src/effects/Tracker.cpp

@@ -126,7 +126,7 @@ std::shared_ptr<Frame> Tracker::GetFrame(std::shared_ptr<Frame> frame, int64_t f
 		// Get the image of the Tracked Object' child clip
 		if (trackedData->ChildClipId() != ""){
 			// Cast the parent timeline of this effect
-			Timeline* parentTimeline = (Timeline *) ParentTimeline();
+			Timeline* parentTimeline = static_cast<Timeline *>(ParentTimeline());
 			if (parentTimeline){
 				// Get the Tracked Object's child clip
 				Clip* childClip = parentTimeline->GetClip(trackedData->ChildClipId());